Steven E Smith

Interests

Research

Evolution of adaptation in plants

Teaching

Plant Biology, Field Botany, Environmental Biology

Courses

Scholarly Contributions

Books

• Soleri, D., Cleveland, D. A., & Smith, S. E. (2019). Food gardening for a changing world. A guide to growing food for healthy people, communities and ecosystems.. CABI.

Chapters

• Brown, J. J., Glenn, E. P., & Smith, S. E. (2014). Feasibility of halophyte domestication for high-salinity agriculture.. In Sabkha Ecosystems: Volume IV: Cash crop halophyte and biodiversity conservation.(pp 73-80).

Journals/Publications

• Smith, S. E., Soleri, D., & Cleveland, D. A. (2022). Food gardens for sustainable diets in the Anthropocene (book chapter). Routledge Handbook of Sustainable Diets.
• Noble, J. A., Seddon, A., Uygun, S., Bright, A., Smith, S. E., Shiu, S., & Palanivelu, R. (2021). The SEEL motif and members of the MYB-related REVEILLE transcription factor family are important for the expression of LORELEI in the synergid cells of the Arabidopsis female gametophyte. Plant Reproduction.
• Monihan, S. M., Magness, C. A., Yadegari, R., Smith, S. E., & Schumaker, K. S. (2016). Arabidopsis CALCINEURIN B-LIKE10 functions independently of the SOS pathway during reproductive development in saline conditions. Plant Physiology, 171, 369-379.
• Monihan, S. M., Magness, C. A., Yadegari, R., Smith, S. E., & Schumaker, K. S. (2016). Arabidopsis CALCINEURIN B-LIKE10 functions independently of the SOS pathway during reproductive development in saline conditions. Plant Physiology.
• Senzen, U., Kopec, D. M., Patterson, A., & Smith, S. E. (2016). Multi-phase US spread and habitat expansion of a post-Columbian invasive, Sorghum halepense.. PLoS ONE, 11(10). doi:10.1371/journal.pone.0164584
• Sezen, U. U., Barney, J. N., Atwater, D. Z., Pederson, G. A., Pederson, J. F., Chandler, J. M., Cox, T. S., Cox, S., Dotray, P., Kopec, D., & others, . (2016). Multi-phase US spread and habitat switching of a post-Columbian invasive, Sorghum halepense. PloS one, 11(10), e0164584.
• Pavliscak, L. L., Fehmi, J. S., & Smith, S. E. (2015). Assessing Emergence of a Long-Lived Monocarpic Succulent in Disturbed, Arid Environments: Evaluating Abiotic Factors in Effective Agave Restoration by Seed. Arid Land Research and Management, 29(1), 98-109.
• Qin, Y., Zhao, L., Skaggs, M. I., Andreuzza, S., Tsukamoto, T., Panoli, A., Wallace, K. N., Smith, S. E., Siddiqi, I., Yang, Z., Yadegari, R., & Palanivelu, R. (2014). ARP6 Controls Female Meiosis In Arabidopsis Partly By Activating DMC1 Expression In Megasporocytes. The Plant Cell, 26(4), 1612-1628.
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  Correspondence: RY and RP. F1000 article recommendation: http://f1000.com/prime/718352855.
• Smith, S. E. (2013). Plant reintroduction in a changing climate. Promises and perils. (Book review.). Restoration Ecology, 21, 661-662.
• Smith, S. E., Mendoza, M. G., Zúñiga, G., Halbrook, K., Hayes, J. L., & Byrne, D. N. (2013). Predicting the distribution of a novel bark beetle and its pine hosts under future climate conditions. Agricultural and Forest Entomology, 15(2), 212-226.
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  Abstract: Understanding the distribution of key biotic elements of forest ecosystems is essential in contemporary forest management and in planning to meet future management needs. Habitat distribution (niche) models based on known occurrences provide geographical structure for such management as the environmental factors change. Bark beetles play critical roles in coniferous forest dynamics in western North America. Among these insects, Dendroctonus rhizophagus Thomas and Bright, which occurs in the Sierra Madre Occidental in Mexico, is unique in that it attacks only immature trees (Pinus spp.) and therefore represents a threat to forest regeneration. We developed current habitat distribution models for D. rhizophagus and its Pinus hosts and projected these to future climate scenarios. Predicted suitable habitat of D. rhizophagus currently covers approximately 119 000 km2 of which approximately 11% is occupied, and overlap with suitable habitat for all Pinus hosts exceeds 99.5%. Some suitable habitat occurs isolated from known D. rhizophagus occurrences in Mexico and the south-western U.S.A. Habitat distribution models were projected to four potential climate scenarios for the period 2040-2060 and this predicted the gains and losses of suitableD. rhizophagus habitat throughout the region. Areas of north-western Mexico maintain large areas of suitableD. rhizophagus and Pinus host habitat in all scenarios. Dispersal to isolated areas of D. rhizophagus habitat appears unlikely. The results of the present study can be used to target D. rhizophagus monitoring and management activities and may serve as a model for the management of other invasive species. © 2013 The Royal Entomological Society.
• Smith, S. E., Mendoza, M. M., Zúñiga, Z., Halbrook, K., Hayes, J. L., & Byrne, D. N. (2013). Predicting the distribution of a novel bark beetle and its pine hosts under future climate conditions.. Agricultural and Forest Entomology, 15, 212-226.
• Soleri, D., Worthington, M., Aragón-Cuevas, F., Smith, S. E., & Gepts, P. (2013). Farmers' Varietal Identification in a Reference Sample of Local Phaseolus Species in the Sierra Juárez, Oaxaca, Mexico. Economic Botany, 67(4), 283-298.
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  Abstract: Farmers' Varietal Identification in a Reference Sample of Local Phaseolus Species in the Sierra Juárez, Oaxaca, Mexico. Farmer-named varieties are often the basis of in situ diversity assessment, collections for ex situ conservation, and on-farm improvement programs. Such varieties play an important role in sustainable agriculture because of their adaptation to local environmental conditions and consumer tastes. The importance of these varieties has stimulated interest in understanding farmers' varietal classifications. We investigated the empirical basis of, and agreement among, farmers' bean variety classification in a community in the Sierra Juárez, Oaxaca, Mexico. A reference sample of 300 local seeds of three Phaseolus species was sorted by nine farmers into named varieties. Nuclear and chloroplast microsatellite markers and seed morphology data were used to a) establish species identities; and test the hypotheses that b) farmer varieties reflect morphological and genetic structures; and c) there is agreement among farmers in variety classification. Because all farmers sorted the same set of seeds the variation in individual farmers' classifications could be documented and compared. Our results indicate an empirical basis for farmer varieties, but without stringent classification rules. Varietal names underestimated diversity present at the community level because of the intravarietal variation present in farmer classifications. There was low classification agreement among farmers, although broad morphological and genetic patterns were present. The variation in farmers' classifications of this Phaseolus diversity resulted in both synonymy and homonymy across classifications. The goal of farmers may not be to maintain the same variety across households, but to form a version of a broad type that best fits their own needs and circumstances at one point in space and time. Thus, in both work with farmers and collections of their Phaseolus varieties for ex situ conservation it should not be assumed that same-named seed lots are redundant units of diversity. Morphological and/or molecular data should, therefore, supplement farmer varietal names in assessments of in situ crop diversity, while ex situ collections would benefit from the inclusion of multiple accessions of the same variety from different farmers, repeated over time. © 2013 The New York Botanical Garden.
• Soleri, D., Worthington, M., Aragón-Cuevas, F., Smith, S. E., & Gepts, P. (2013). Farmers' varietal identification in a reference sample of local Phaseolus species in the Sierra Juarez, Oaxaca, Mexico.. Economic Botany, 64, 282-298.
• Routson, K. J., Volk, G. M., Richards, C. M., Smith, S. E., Nabhan, G. P., & Wyllie, V. (2012). Genetic variation and distribution of pacific crabapple. Journal of the American Society for Horticultural Science, 137(5), 325-332.
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  Abstract: Pacific crabapple [Malus fusca (Raf.) C.K. Schneid.] is found in mesic coastal habitats in Pacific northwestern North America. It is one of four apple species native to North America. M. fusca is culturally important to First Nations of the region who value and use the fruit of this species as food, bark and leaves for medicine, and wood for making tools and in construction. However, little is known about either distribution or genetic diversity of this species. To correct this deficiency, we used habitat suitability modeling to map M. fusca habitat types with species occurrence records. The species apparently occupies at least two distinct climate regions: a colder, drier northern region and a warmer, wetter southern region. Total area of modeled habitat encompasses ≈ 356,780 km2 of low-lying areas along the Pacific coast. A total of 239 M. fusca individuals sampled from across its native range were genetically compared using six microsatellite markers to assess for possible geographic structuring of genotypes. The primers amplified 50 alleles. Significant isolation by distance was identified across the ≈ 2600 km (straight line) where samples were distributed. These results may help establish priorities for in situ and ex situ M. fusca conservation.
• Qin, Y., Wysocki, R. J., Somogyi, A., Feinstein, Y., Franco, J. Y., Tsukamoto, T., Dunatunga, D., Levy, C., Smith, S. E., Simpson, R., Gang, D., Johnson, M. A., & Palanivelu, R. -. (2011). Sulfinylated azadecalins act as functional mimics of a pollen germination stimulant in Arabidopsis pistils. The Plant journal : for cell and molecular biology, 68(5).
• Smith, S. E., Arredondo, T., Aguiar, M., Huber-Sannwald, E., Alpuche, A., Aguado, A., Grageda, O. A., Halbrook, K., & Bottini, C. (2009). Fine-scale spatial genetic structure in perennial grasses in three environments. Rangeland Ecology and Management, 62(4), 356-363.
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  Abstract: Past research has shown that changes in grazing-resistance traits may be associated with genetic changes in plant populations.Little is known about spatial genetic relationships within plant populations (spatial genetic structure) and any grazing effects on these relationships. Here we present observations of the fine-scale spatial genetic structure in three grass species in semiarid environments (Arizona, Mexico, and Argentina). In each environment, populations of a dominant grass species were sampled from two sites with contrasting livestock grazing histories.Plant genotypes were described with the use of amplified fragment length polymorphism markers. In Arizona, populations of sideoats grama (Bouteloua curtipendula var. caespitosa Gould and Kapadia) differed in that one has never experienced livestock grazing, whereas cattle have grazed the other. In the other two environments, populations exposed to long-term heavy grazing were examined, along with those that experienced either moderate grazing (Mexico, blue grama [Bouteloua gracilis {Willd. ex Kunt} Lag. ex Griffiths]) or extended exclusion of livestock (Argentina [Poa ligularis Nees ex Steud.]). Based on independent analysis of each population, we observed no differences in average gene diversity between populations of each species. With the use of analysis of molecular variance we found slight but significant genetic differentiation between populations with different grazing histories in Arizona and Argentina. Significant genetic structure was present in all populations and indicated an inverse relationship between spatial and genetic distance. Interestingly, this relationship was most pronounced in the cattle-free sideoats grama population, suggesting larger genetic neighborhood areas in the absence of livestock. Less distinct differences in spatial genetic structure associated with grazing history were evident in the other two species. We hypothesize that livestock grazing may lead to increased homogeneity in genetic structure at the landscape scale. Effectively examining this hypothesis presents many experimental challenges.
• Hayes, J. L., Johnson, P. L., Eglitis, A., Scott, D. W., Spiegel, L., Schmit, C. L., & Smith, S. E. (2008). Response of bark and woodboring beetles to host volatiles and wounding on western juniper. Western Journal of Applied Forestry, 23(4), 206-215.
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  Abstract: In central Oregon, management of western juniper (Juniperus occidentalis var. occidentalis Hook.) has included use of prescribed fire and mechanical removal. After these treatments, several species of bark and woodboring beetles have been observed on treated trees and also occasionally on trees outside management areas, suggesting that these insects might contribute to juniper mortality. In this 2-year (2002-2003) study, we identified bark and woodboring beetles that attack western juniper along with associated beetle predators and examined whether these insects can be manipulated for use in juniper management. Using funnel traps and sticky traps on trees wounded by pruning or treated with host volatiles (juniper berry oil, cade oil, and ethanol) that may attract insects, we captured beetles in the families Buprestidae, Cerambycidae, and Scolytidae (20 species in 17 genera) and known predators in the families Cleridae and Trogositidae (8 species in 7 genera). Cedar bark beetles (Phloeosinus spp.) were the most prevalent insects captured on trees treated with host volatiles and/or wounded. Treatments that included ethanol plus wounding were most attractive to these beetles. However, there was no obvious insect-caused damage or mortality of treated trees in either year of this study.
• Johnson, P. L., Hayes, J. L., Rinehart, J., Sheppard, W. S., & Smith, S. E. (2008). Characterization of two non-native invasive bark beetles, Scolytus schevyrewi and Scolytus multistriatus (Coleoptera: Curculionidae: Scolytinae). Canadian Entomologist, 140(5), 527-538.
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  Abstract: Scolytus schevyrewi Semenov, the banded elm bark beetle, and S. multistriatus Marsham, the smaller European elm bark beetle, are morphologically similar. Reliance on adult external morphological characters for identification can be problematic because of wide within-species variability and the need for good-quality specimens. The inability to identify developmental stages can also hamper early-detection programs. Using two character identification systems, genitalic (aedeagus) morphology, and DNA markers (random amplified polymorphic DNA polymerase chain reaction (RAPD-PCR)) to distinguish S. schevyrewi from S. multistriatus, we examined specimens from geographically distinct populations of both species collected from infested host trees or semiochemical-baited funnel traps. We found that aedeagus morphology can be used to identify the two species. The use of two oligonucleotide primers in the RAPD-PCR analysis yielded distinct DNA banding patterns for the two species. Species identification using RAPD-PCR analysis was validated by a blind test and used to make species identifications of larval specimens. These tools improve the ability to differentiate between S. schevyrewi and S. multistriatus at immature and adult stages, and could be developed and used for other scolytines as well. © 2008 Entomological Society of Canada.
• Smith, S. E., Fendenheim, D. M., & Halbrook, K. (2006). Epidermal conductance as a component of dehydration avoidance in Digitaria californica and Eragrostis lehmanniana, two perennial desert grasses. Journal of Arid Environments, 64(2), 238-250.
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  Abstract: Epidermal conductance (gmin) is water lost through the cuticle and stomata of plants when stomatal conductance is minimal. Low gmin may affect survival of perennial grasses by maintaining tissue hydration during drought. If true, populations from environments where drought is severe may exhibit reduced gmin compared to those from less arid environments. Success of invasive grasses may also be associated with reduced gmin compared to non-invasive competitors. Using plants grown in a single environment, we measured gmin of leaves from populations of Digitaria californica from environments with similar annual precipitation but differing in average drought severity (southern Arizona and western Texas, USA), and a population of the exotic species Eragrostis lehmanniana that has invaded sites occupied by D. californica in Arizona. Epidermal conductance was lower in the D. californica population from the more arid environment (Texas). Likewise, g min was lower in E. lehmanniana than in the Arizona D. californica population. Shoot biomass production as a fraction of gmin was higher in E. lehmanniana than in the D. californica populations and was higher in the Texas D. californica population than in the Arizona population. This suggests that low gmin may be a component of drought avoidance in these grasses. © 2005 Elsevier Ltd. All rights reserved.
• Ward, J. P., Smith, S. E., & McClaran, M. P. (2006). Water requirements for emergence of buffelgrass (Pennisetum ciliare). Weed Science, 54(4), 720-725.
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  Abstract: The ability of an invasive species to acquire and use a limiting resource during critical life history stages governs its ability to establish and persist within an environment. Arid environments are generally considered more resistant to invasion and are defined by low and sporadic precipitation. Warm-season grasses are most susceptible to mortality during seedling emergence, but water requirements for emergence are rarely known. We examined the ability of the often invasive warm-season grass, buffelgrass, to emerge given a range of simulated precipitation delivered on 2, 3, and 4 consecutive days with the use of a line-source irrigation system in a glasshouse. The minimum amount of water required for buffelgrass emergence was observed to be 6.3 mm (3.14 mm on 2 consecutive days). With the use of probit analysis, the median emergence response (0.5 emergence probability) was predicted to require 17.4-19.9 mm of water. Emergence was concentrated within the first 5 days following initial simulated precipitation with the probability of new emergence highest on Days 3 and 4. Over the period from 1949-2001 in Tucson, Arizona within the Sonoran Desert, the total number of consecutive rainy-day sequences meeting the minimum per-day precipitation levels for a median and minimum emergence response was 27 and 92, respectively. Precipitation sufficient to result in emergence of 50% of viable buffelgrass caryopses has occurred in Tucson in about 1 of 2 years over this period. We compare the soil water requirements for emergence of buffelgrass to other perennial species in the Sonoran Desert and suggest that the invasion success of buffelgrass is due in part to its ability to emerge following relatively low precipitation levels.
• Fernandez-Giménez, M. E., & Smith, S. E. (2004). Research observation: Nitrogen effects on Arizona cotton-top and Lehmann lovegrass seedlings. Journal of Range Management, 57(1), 76-81.
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  Abstract: We compared the responses of seedlings of introduced Lehmann lovegrass (Eragrostis Lehmanniana Nees) and a native perennial grass, Arizona cottontop (Digitaria californica (Benth.) Henr.) to 7 nitrogen and 2 water treatments to determine if Lehmann lovegrass displayed greater growth or nitrogen use efficiency than Arizona cottontop. After 8 weeks, the lovegrass seedlings had greater shoot N concentrations (2.07 vs. 1.20%), and lower C:N ratios (27.7 vs. 49.6) than Arizona cottontop seedlings. Arizona cottontop seedlings produced more biomass per plant (1.09 vs. 0.31g), exhibited greater nitrogen use efficiency (63 vs. 39%), and tolerated high N levels better. Arizona cottontop may be a superior N competitor under both N-limited and high N conditions, while Lehmann lovegrass may outcompete Arizona cottontop at moderate N levels.
• Veatch, M. E., Smith, S. E., & Vandemark, G. (2004). Shoot biomass production among accessions of Medicago truncatula exposed to NaCl. Crop Science, 44(3), 1008-1013.
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  Abstract: Increased salt tolerance would improve utilization of salt-sensitive crop plants such as alfalfa (Medicago sativa L.). In order for selection for salt tolerance to be more efficient, it is useful to know whether improved productivity under saline conditions is due to unique physiological responses to salinity or merely the carry over of increased yield that was selected for in a nonsaline environment. Medicago truncatula Gaertn., a self-pollinated relative of alfalfa, was used to examine the response of specific genotypes across a range of salinities. This was done by evaluating the change in fresh shoot biomass production of greenhouse-grown mature plants and seedlings of different accessions of M. truncatula in response to four levels of salinity imposed as NaCl. Those accessions with the highest fresh shoot biomass production under nonsaline irrigation also had the highest fresh shoot biomass production under all salinity levels. The high correlation between an accession's fresh shoot biomass under nonsaline and saline irrigation indicate no unique physiological adaptation to salinity in the accessions of M. truncatula evaluated.
• Soleri, D., & Smith, S. E. (2002). Rapid estimation of broad sense heritability of farmer-managed maize populations in the Central Valleys of Oaxaca, Mexico, and implications for improvement. Euphytica, 128(1), 105-119.
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  Abstract: A method for rapid estimation of broad sense heritability (H) was applied in farmers' maize fields in two communities in Oaxaca, Mexico. Plant and ear traits were documented and H estimates compared with narrow sense heritability (h2) from family analysis and published estimates. Absolute values of H estimates were larger than h2 estimates from this study and the literature. Relative ranking by trait was the same as in the literature, though not the same as rankings of h2 estimates generated in this study. With an understanding of its limitations, this rapid, economical estimation procedure could provide useful initial information especially for collaborative crop improvement work between researchers and farmers or farming communities on-farm, a plant breeding context for which little empirical information is available.
• Vaughan, L. V., MacAdam, J. W., Smith, S. E., & Dudley, L. M. (2002). Root growth and yield of differing alfalfa rooting populations under increasing salinity and zero leaching. Crop Science, 42(6), 2064-2071.
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  Abstract: Accumulation of salinity in the root zone can be detrimental to sustained crop production. Irrigation, even with moderately saline water, pushes accumulated salts deeper into the root zone, allowing roots to proliferate in regions of relatively low salinity. Two alfalfa (Medicago sativa L.) subpopulations with low- and high-fibrous rooting characteristics, MnPL-9-LF and MnPL-9-HF, were used to test the effectiveness of increased rooting on yield when plants were irrigated with saline water but without leaching. Treatments were three levels of heterogeneous root zone salinity predicted by the SOWACH model to represent 10, 20, and 30 yr of irrigation with saline water. Plants were grown for five successive harvests in 10-cm-diam., 130-cm-deep cylinders. The treatments were constructed with NaCl and gypsum. As soil became depleted to 50% extractable water, irrigation water with an electrical conductivity (EC) of 2.8 dS m-1 was applied. By the fifth harvest, soil solution EC from the top to the bottom of the profile ranged from 3 to 12 dS m-1 for the control and from 3 to 23 dS m-1 for the highest salinity treatment. Root production of the high-fibrous root type was stimulated more at low and medium salinity than that of the low-fibrous root type. Across salinity treatments, final root length density (cm root length per cm3 soil volume) was 24% higher for the high-fibrous root type, and herbage yield of the high-fibrous root type was 14% higher than that of the low-fibrous root type. Differential rooting was greatest in the upper half of the root zone. High fibrous rooting in alfalfa is a trait with potential usefulness as a salinity stress avoidance mechanism.
• Idris, A. M., Smith, S. E., & Brown, J. K. (2001). Ingestion, transmission, and persistence of Chino del tomate virus (CdTV), a new world begomovirus, by old and new world biotypes of the whitefly vector Bemisia tabaci. Annals of Applied Biology, 139(1), 145-154.
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  Abstract: Two whitefly biotypes of Bemisia tabaci, from either the Eastern or Western Hemisphere, respectively, were compared with respect to their competency to ingest and their efficiency to transmit the New World begomovirus, Chino del tomate virus (CdTV). The AZ A biotype of B. tabaci originates from the arid southwestern USA and northwestern Mexico, while the B biotype has an origin in the Middle East or Northern Africa. The ability of these two vector biotypes to ingest and subsequently to transmit CdTV were evaluated for an acquisition-access period (AAP) that ranged from 0 to 72 h, followed by a 48 h inoculation-access period (IAP). Individual adult whiteflies were monitored for CdTV ingestion using polymerase chain reaction (PCR) to detect the viral coat protein gene (AV1 ORF), and transmission efficiency (frequency) was determined by allowing potentially viruliferous whiteflies access to tomato seedlings following each experimental AAP. PCR results for individual adult whiteflies indicated that CdTV was ingested from infected tomato plants by both biotypes 93% of the time. Transmission frequencies by both vector biotypes increased with longer AAPs. However, the AZ A biotype transmitted CdTV 50% of the time, compared to only 27% for the B biotype. Evidence that virus was ingested with equal competency by the A and B biotypes confirmed that both vectors were capable of ingesting CdTV from tomato at the same frequency, even when the AAP was 0.5 h. Consequently, either the acquisition and/or transmission stages of the pathway, rather than ingestion competency, were responsible for differences in vector-mediated transmissibility. Detection frequency of CdTV, after 48 h AAP, by PCR in single females of AZ B biotype was significantly higher than males.
• Roundy, B. A., Heydari, H., Watson, C., Smith, S. E., Munda, B., & Pater, M. (2001). Summer establishment of Sonoran Desert species for revegetation of abandoned farmland using line source sprinkler irrigation. Arid Land Research and Management, 15(1), 23-39.
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  Abstract: A line source sprinkler was used to determine water requirements of adapted species for revegetation of abandoned farmlands in the Sonoran Desert of southern Arizona. Six grass and seven woody species were seeded on a fine-sandy soil initially at field capacity water content during the summers of 1992 and 1993 in Tucson, Arizona. The line source sprinkler created a greater difference in soil water availability between irrigated and unirrigated soils than within the irrigation gradient itself Initial irrigation was followed by periods of summer rainfall in both years. Species emergence and establishment varied with amount and timing of irrigation and summer rainfall. After the initial 14 days of irrigation in 1992 and 11 days in 1993, soil water availability was intermittent in the surface soil but was consistently high at depths greater than 18 cm. Emergence was more sensitive to the irrigation gradient than was plant survival. Most species established successfully with at least 210 mm of irrigation plus precipitation. A possible strategy for establishing many of these species on abandoned farmland would be to fill the soil profile to field capacity by irrigating on consecutive days until emergence is observed. Direct seeding without irrigation or water concentration is not recommended due to the erratic and limited nature of summer rainfall on abandoned farmland in the lower Sonoran Desert.
• Cleveland, D. A., Soleri, D., & Smith, S. E. (2000). A biological framework for understanding farmers' plant breeding. Economic Botany, 54(3), 377-394.
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  Abstract: We present a framework for understanding farmer plant breeding (including both choice of varieties and populations and plant selection) in terms of the basic biological model of scientific plant breeding, focusing on three key components of that model: 1) genetic variation, 2) environmental variation and variation of genotype-by-environment interaction, and 3) plant selection. For each of these concepts we suggest questions for research on farmers' plant breeding (farmers' knowledge, practice, and crop varieties and growing environments). A sample of recent research shows a range of explicit and implicit answers to these questions which are often contradictory, suggesting that generalizations based on experience with specific varieties, environments or farmers may not be valid. They also suggest that farmers' practice reflects an understanding of their crop varieties and populations that is in many ways fundamentally similar to that of plant breeders; yet, is also different, in part because the details of their experiences are different. Further research based on this framework should be valuable for participatory or collaborative plant breeding that is currently being proposed to reunite farmer and scientific plant breeding.
• Smith, S. E., Mosher, R., & Fendenheim, D. (2000). Seed production in sideoats grama populations with different grazing histories. Journal of Range Management, 53(5), 550-555.
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  Abstract: Frequent and intense defoliation of grasses has been associated with the evolution of 'grazing morphotypes' that exhibit a variety of vegetative traits correlated with improved grazing resistance. While recovery from a seed bank is not considered an important grazing resistance mechanism, relatively little is actually known regarding seed (caryopsis) production in grazing morphotypes of caespitose grasses. The goal of this research was to compare components of seed production in 2 populations of sideoats grama (Bouteloua curtipendula var. caespitosa Gould and Kapadia) from nearby sites with different histories of livestock grazing. This was done using vegetative propagules of genotypes from both populations in a greenhouse study. The study was conducted in 2 flowering seasons under conditions considered favorable for seed production. The population exposed to livestock grazing showed a genetically based decrease in seed production relative to the ungrazed population. Lower seed production per plant in the grazed population was at least partially due to reduced numbers of tillers and panicles per plant and spikes per panicle that may be associated with selection for grazing tolerance. The grazed population also exhibited lower average seed production per spike indicating lower inherent floral fertility. Seed production was not closely correlated with vegetative traits associated with increased grazing tolerance, nor was there evidence of obvious physiological trade-offs related to decreased seed production in the grazed population. Lower seed production potential in populations of sideoats grama intensively grazed by livestock may lead to reduced potential for seedling colonization.
• Smith, S. E., Riley, E., Tiss, J. L., & Fendenheim, D. M. (2000). Geographical variation in predictive seedling emergence in a perennial desert grass. Journal of Ecology, 88(1), 139-149.
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  Abstract: 1. Mechanisms that link germination and emergence to environmental cues associated with seedling success (predictive germination) would be expected to evolve when seedlings have a greater mortality risk than seeds, but may be less important in perennial plants than in annual plants. 2. We investigated variation in predictive seedling emergence among divergent populations of a short-lived perennial desert grass, Digitaria californica, from sites that differed in climatic and edaphic factors. This species is native to environments in which the amount and duration of adequate soil moisture may control germination and seedling establishment success. 3. We utilized a special irrigation system that permits application of a range of amounts of water within a single experiment in a glasshouse. Emergence data were subjected to probit and survival analyses to describe differences among the populations in response to applied water. 4. Significant variation in predictive emergence was shown to exist among populations of D. californica when measured as amount of water required for 50% emergence following 3 days of water application, or as time required to achieve this level of emergence. Both climatic and soil characteristics were important with populations that originated from sites with less summer precipitation, and soils with higher water-holding capacity tended to have lower water requirements for emergence. 5. The report demonstrates the existence of subtle variation in predictive emergence among populations of a perennial grass representing a relatively narrow range of ecological amplitude. It also establishes the usefulness of line-source irrigation and probit analysis procedures in studying seedling emergence behaviour.
• Soleri, D., Smith, S. E., & Cleveland, D. A. (2000). Evaluating the potential for farmer and plant breeder collaboration: A case study of farmer maize selection in Oaxaca, Mexico. Euphytica, 116(1), 41-57.
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  Abstract: Formal plant breeders could contribute much to collaboration with farmers for improving crop varieties for local use. To do so outside researchers must have some understanding of local selection practices and their impact on crop populations in terms of the genetic theory underlying plant breeding. In this research we integrated methods from social and biological sciences to better understand selection and its consequences from farmers' perspectives but based on the concepts used by plant breeders. Among the households we worked with, farmers' selection practices were not always effective yet they understood the reasons for this and had no expectations for response to selection in some traits given the methods available to them. Farmers' statements, practices and genetic perceptions regarding selection and the genetic response of their maize populations to their selection indicate selection objectives different than may be typically assumed, suggesting a role for plant breeder collaboration with farmers.
• Smith, S. E. (1998). Variation in response to defoliation between populations of Bouteloua curtipendula var. caespitosa (Poaceae) with different livestock grazing histories. American Journal of Botany, 85(9), 1266-1272.
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  PMID: 21685013;Abstract: Distinctive plant growth and development have been associated with resistance to defoliation by herbivores. Descriptions of resistance (tolerance/avoidance) strategies are common, although little is known about genetic variation affecting their expression in natural plant communities. This research compared response to three frequencies of defoliation in populations of Bouteloua curtipendula var. caespitosa from Arizona with different histories of exposure to domestic herbivores. One population occurs on a site that has likely been unaffected by large herbivores including cattle, while the other has been regularly grazed by cattle. Mixed-model analysis of variance was used to examine variation in traits associated with defoliation resistance. Data were collected in a 168-d greenhouse experiment using ramets of 15 genets from each population. Mortality was lower in the cattle-impacted population, suggesting improved defoliation resistance. This was associated with increased production of tillers with lower mass following defoliation. Plasticity was observed for all traits in response to different defoliation frequencies. The cattle-free population exhibited significant genetic variation for plasticity affecting leaf blade angle, while little variation was noted for this trait in the cattle-impacted population. Evidence of reduced genetic variation within the cattle-impacted population was noted for traits associated with defoliation resistance. In general, these observations are consistent with expectations following selection for resistance to defoliation.
• Smith, S. E., Kuehl, R. O., Ray, I. M., Hui, R., & Soleri, D. (1998). Evaluation of simple methods for estimating broad-sense heritability in stands of randomly planted genotypes. Crop Science, 38(5), 1125-1129.
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  Abstract: Inexpensive estimates of broad-sense heritability (BSH) may be valuable in plant breeding. This research evaluated two methods for estimating BSH with data from stands of equidistantly spaced genotypes. Both methods depend on the assumption that genetic and environmental contributions to plot variance (plot = group of contiguous plants) change at different rates as plot size changes if genetic variation is distributed randomly. For the method proposed by V.J. Shrikhande, variances among plot means are computed and least-squares regression used to estimate environmental and genetic variances and the change in a plot variance with changes in plot size. The other method involves the same approach, but uses a two-parameter model suggested by G.H. Freeman but not previously used to estimate BSH. Both methods produce biased BSH estimates since genotypic and genotypic x environmental components of variation are inseparable. Our objectives were to: (i) develop software to calculate variances for the methods, and (ii) compare BSH estimates generated using these methods with each other and with those from analysis of variance (ANOVA) of data from families grown in the same environment. Data were from a perennial herb, Sphaeralcea emoryi Torr. grown in Tucson, AZ. Shrikhande's method produced parameter estimates with large variances and BSH estimates that averaged 3.6 times larger than those from Freeman's method. Only BSH estimates from Freeman's method agreed well with those from ANOVA for most traits. Freeman's method may be useful for rapidly and inexpensively generating BSH estimates in a variety of situations, especially when traditional genetic analysis are difficult.
• Livingston, M., Roundy, B. A., & Smith, S. E. (1997). Association of overstory plant canopies and native grasses in southern Arizona. Journal of Arid Environments, 35(3), 441-449.
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  Abstract: In arid regions, overstory plants may influence establishment and persistence of understory species. Identifying relationships between overstory and understory plants may increase success of revegetation efforts. This research considered whether three desirable grasses native to the Sonoran Desert, Arizona cottontop (Digitaria californica), plains lovegrass (Eragrostis intermedia) and bush muhly (Muhlenbergia porteri), differ in density or cover under overstory species compared to open areas. Selection of sites in southern Arizona (two or three per species) was based on abundance of study species and elevation. Density and cover of Arizona cottontop and plains lovegrass was highly variable between canopied and open areas among sites. Bush muhly had greater density and cover under canopies at all sites. No association was noted between precipitation or elevation and density or cover ratios. Identifying understory species well-adapted to shaded sites may aid in determining the best use of existing vegetation for revegetation in this region.
• Wissuwa, M., & Smith, S. E. (1997). Morphological and physiological characteristics associated with tolerance to summer irrigation termination in alfalfa. Crop Science, 37(3), 704-711.
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  Abstract: Deliberately withholding irrigation to alfalfa (Medicago sativa L.) during summer, a management strategy referred to as summer irrigation termination (SIT), has been suggested to conserve water in long-season desert environments. Summer irrigation termination may reduce productivity of alfalfa stands, although such effects may be lessened if cultivars with improved tolerance to SIT could be developed. This study was conducted to identify characteristics associated with low crown mortality as the primary component of tolerance to SIT. Using such traits in selection may be superior to direct selection for post-SIT yield, a trait potentially characterized by low heritability. Single spaced nondormant alfalfa plants were grown in a field trial in Tucson, AZ, and subjected to two SIT treatments during two years (Treatment 1, 84 d in 1994 and Treatment 2, 42 d in 1994 and 75 d in 1995). Traits evaluated prior to SIT (forage yield, stem number, plant height, leaf area, and root diameter) were not significantly associated with crown mortality. Significant but weak correlations were detected between crown mortality and days to wilting (r = -0.25*) and plant height during SIT (r = -0.29*). Accumulation of osmotically active substances, such as proline and sucrose, was not related to crown mortality. However, crown mortality was significantly correlated with concentration of total nonstructural carbohydrates (TNC) in crown tissue on Days 28 (r = -0.57*) and 35 (r = -0.79*) of SIT. The TNC reserves may be essential for continued respiration during periods of drought. Depletion of TNC reserves could have caused plant death in intolerant plants. Concentrations of TNC in crown tissue may represent a criterion in indirect selection for decreased crown mortality during SIT in selected environments.
• Wissuwa, M., Smith, S. E., & Ottman, M. J. (1997). Crown moisture and prediction of plant mortality in drought-stressed alfalfa. Irrigation Science, 17(2), 87-91.
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  Abstract: Withholding alfalfa (Medicago sativa L.) irrigations during the summer, a practice referred to as summer irrigation termination (SIT), can conserve substantial amounts of water in long-season desert environments; however, plant mortality associated with SIT may be substantial. Proper timing of re-irrigation is critical for minimizing mortality and yield reductions following SIT. Procedures that would permit probable mortality prediction during drought stress would improve management efficiency with SIT. This study was conducted to determine (1) whether plant mortality occurs once the moisture content of the plant woody stem portions (crown) falls below some critical threshold and (2) if such a threshold could be used to predict the likelihood of plant mortality during SIT. Crown samples were taken from single, spaced, field-grown plants in Tucson, Arizona, at the end of a 84-day SIT period in 1994. A crown moisture content of about 42% was identified as a likely threshold critical for crown tissue SIT survival. This value was then used to predict whole-plant mortality of alfalfa grown in solid-seeded plots comparable to commercial fields. Crown samples were taken at five locations within the field along a solid gradient that was related to plant mortality. At each sampling location, the proportion of samples with less than 42% crown moisture was used to predict plant mortality. Predicted mortality slightly overestimated actual mortality but differences between predicted and observed mortality were significant for only one of five sampling locations. Alfalfa growers may be able to use this simple method of crown moisture determination to prevent permanent yield reductions by initiating irrigation before substantial portions of crowns fall below the threshold moisture content of 42%.
• Hotchkiss, J. R., Smith, S. E., & Miller, W. B. (1996). Persistence and single-plant productivity in nondormant alfalfa. Crop Science, 36(2), 336-340.
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  Abstract: Plant mortality is generally substantial in alfalfa (Medicago sativa L.) fields both at establishment and during the productive life of the stand. Most research has examined the effects of mortality on alfalfa yield per unit area. Consequences of mortality within a population on single-plant productivity have received relatively little attention. Understanding the basis for this mortality could affect management practices and the breeding and testing of alfalfa cultivars. The objective of this study was to describe agronomic, morphological, and physiological traits associated with persistence in nondormant alfalfa. This was accomplished by comparing two populations of S1 progenies derived from 60 surviving 6-yr-old plants from a commercial field of 'CUF-101' (= field-derived [FD] population) and 60 greenhouse-grown CUF-101 plants (= greenhouse-derived [GHD] population) in field and greenhouse trials at Tucson, AZ. In a field trial, crown mortality, as measured by the percent live stems, did not differ significantly between the populations. Total forage yield, yield in winter and spring, and stem elongation rates were significantly greater in the GHD population. Root weight, total plant weight, root/shoot weight ratio, and concentration of total nonstructura) carbohydrates in the root were significantly greater in the FD population in a greenhouse trial. Differences observed between the two populations are consistent with the elimination of presumably less competitive plants with smaller root systems and plants intolerant of grazing in the winter and early spring. This research suggests that mortality within stands of nondormant alfalfa is less likely for plants with larger roots and generally slower growth patterns that are typically associated with increased fall dormancy.
• Keys, R. N., Buchmann, S. L., & Smith, S. E. (1995). Pollination effectiveness and pollination efficiency of insects foraging Prosopis velutina in south-eastern Arizona. Journal of Applied Ecology, 32(3), 519-527.
• Keys, R. N., Smith, S. E., & Mogensen, H. L. (1995). Variation in generative cell plastid nucleoids and male fertility in Medicago sativa. Sexual Plant Reproduction, 8(5), 308-312.
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  Abstract: Biparental inheritance of plastids has been documented in numerous angiosperm species. The adaptive significance of the mode of plastid inheritance (unior biparental) is poorly understood. In plants exhibiting paternal inheritance of plastids, DNA-containing plastids in the microgametophyte may affect survival or growth of the gametophyte or the embryo. In this study the number of plastids containing DNA (nucleoids) in generative cells and generative cell and pollen volumes were evaluated in a range of genotypes of Medicago sativa (alfalfa). M. sativa exhibits biparental inheritance of plastids with strong paternal bias. The M. sativa genotypes used were crossed as male parents to a common genotype and the relationships between the gametophytic traits measured and male reproductive success were assessed. Generative cell plastid number and pollen grain size exhibited opposing associations with male fertility. Path analysis showed that generative cell plastid number was negatively associated with male fertility. This study provides evidence that there may be a competitive advantage at fertilization afforded sperm that have minimized their organelle content. The apparent lack of strong selection for reduced plastid number in generative cells of M. sativa may be a reflection of the diminished importance of reproductive success due to its perenniality or its long use in cultivation. © 1995 Springer-Verlag.
• Keys, R. N., Smith, S. E., Mogensen, H., & Small, E. (1995). Microgametophytic plastid nucleoid content and reproductive and life history traits of tribe Trifolieae (Fabaceae). Plant Systematics and Evolution, 196(1-2), 89-98.
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  Abstract: Microgametophytic plastid nucleoids were quantified for 18 species representing the four core genera of the tribe Trifolieae (Fabaceae), Medicago, Melilotus, Trigonella, and Trifolium. Generative cells of all taxa contained nucleoids, establishing that biparental plastid inheritance is common in the Trifolieae. Nucleoid number and volumes of pollen grains and generative cell nuclei differed among taxa. Nucleoid number was positively correlated with pollen grain and generative cell nuclear volumes, flower size and style length. These relationships disappeared after adjusting nucleoid number for pollen grain and generative cell nuclear volumes. Adjusted nucleoid numbers provided no evidence to support hypotheses that plastid content is associated with ploidy level, mating system, perenniality or size of the reproductive apparatus. © 1995 Springer-Verlag.
• Livingston, M., Roundy, B. A., & Smith, S. E. (1995). Association of native grasses and overstory species in southern Arizona. General Technical Report - US Department of Agriculture, Forest Service, 202-208.
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  Abstract: This research considered whether three native grasses, Arizona cottontop (Digitaria californica), plains lovegrass (Eragrostis intermedia), bush muhly (Muhlenbergia porteri), and other herbaceous understory species have greater density and cover under overstory species compared to open areas. Arizona cottontop had either significantly greater, less, or similar density under canopies compared to open areas. Arizona cottontop had significantly greater or similar cover among canopied and open areas. Plains lovegrass had significantly lower density and cover under velvet mesquite (Prosopis velutina) than in open areas at one site, while no significant differences were observed among canopied and open areas at a higher elevation site. Bush muhly had greater density and cover under canopies for all sites. -Authors
• Rusche, M., Mogensen, H. L., Zhu, T., & Smith, S. E. (1995). The zygote and proembryo of alfalfa: quantitative, three-dimensional analysis and implications for biparental plastid inheritance. Protoplasma, 189(1-2), 88-100.
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  Abstract: Genetic studies have demonstrated biparental inheritance of plastids in alfalfa. The ratio of paternal to maternal plastids in the progeny varies according to the genotypes of the parents, which can be classified as strong or weak transmitters of plastids. Previous cytological investigations of generative cells and male gametes have provided no consistent explanation for plastid inheritance patterns among genotypes. However, plastids in the mature egg cells of a strong female genotype (6-4) were found to be more numerous and larger than in mature eggs of a weak female genotype (CUF-B), and the plastids in 6-4 eggs are positioned equally around the nucleus. In CUF-B, the majority of plastids are positioned below (toward the micropyle) the mid level of the nucleus, which is the future division plane of the zygote. Since only the apical portion of the zygote produces the embryo proper, plastids in the basal portion were predicted to become included in the suspensor cells and not be inherited. In the present study, we examined zygotes and a two-celled proembryo from a cross between CUF-B and a strong male genotype (301), a cross that results in over 90% of the progeny possessing paternal plastids only. Our results indicate that the distribution of plastids observed in the CUF-B egg cell is maintained through the first division of the zygote. Further, paternal plastids are similarly distributed; however, within the apical portion of the zygote and in the apical cell of the two-celled proembryo, the number of paternal plastids is typically much greater than the number of maternal plastids. These findings suggest that maternal and paternal plastid distribution within the zygote is a significant factor determining the inheritance of maternal and paternal plastids in alfalfa. © 1995 Springer-Verlag.
• Smith, S. E., Guarino, L., Al-Doss, A., & Conta, D. M. (1995). Morphological and agronomic affinities among Middle Eastern alfalfas - Accessions from Oman and Yemen. Crop Science, 35(4), 1188-1194.
• Soleri, D., & Smith, S. E. (1995). Morphological and phenological comparisons of two Hopi maize varieties conserved in situ and ex situ. Economic Botany, 49(1), 56-77.
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  Abstract: Over the last twenty-five years, crop genetic resources (CGR) have been preserved in genebanks around the world for use by formal plant breeders. Recently conservation of folk crop varieties for direct use by the farmer-breeders of traditional agricultural communities has been suggested as another purpose for CGR conservation. While both in and ex situ CGR conservation programs have been proposed to meet the needs of formal plant breeders and farming communities, the needs and goals of the two groups are different. Formal breeders seek maximum allelic diversity while farmer-breeders are interested in both diversity and population structure that provide local adaptation. Based on the morphological and phenological data analyzed for this study of two Hopi maize varieties conserved in and ex situ, it appears that both genetic shift and genetic drift have occurred ex situ, and that populations conserved ex situ are different from those maintained in situ. These findings suggest that CGR conservation strategies must be re-evaluated in light of the specific conservation goals that are sought. © 1995 The New York Botanical Garden.
• Cleveland, D. A., Soleri, D., & Smith, S. E. (1994). Do folk crop varieties have a role in sustainable agriculture?. BioScience, 44(11), 740-751.
• Keys, R. N., & Smith, S. E. (1994). Mating system parameters and population genetic structure in pioneer populations of Prosopis velutina (Leguminosae). American Journal of Botany, 81(8), 1013-1020.
• Smith, S. E., Johnson, D. W., Conta, D. M., & Hotchkiss, J. R. (1994). Using climatological, geographical, and taxonomic information to identify sources of mature-plant salt tolerance in alfalfa. Crop Science, 34(3), 690-694.
• Brahim, K., & Smith, S. E. (1993). Annual medic establishment and the potential for stand persistence in southern Arizona. Journal of Range Management, 46(1), 21-25.
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  Abstract: Winter annual legumes in the genus Medicago (medics) are native to arid sites in North Africa and the Middle East and have been successfully introduced into arid and semiarid rangelands. The objective of this study was to evaluate the potential of establishing medics in areas of the southwestern US receiving between 100-200 mm winter precipitation (November-May). Five accessions from four species M. laciniata, M. littoralis, M. polymorpha, and M. truncatula that could avoid drought were identified in a preliminary screening nursery. These accessions established and produced seed in 1989-90 in a field plot at Tucson, Ariz., with 125 mm winter precipitation. Less than 5% of all seed produced by these accessions germinated following summer precipitation. Plant re-establishment in the winter 1990-91 (181 mm precipitation) from pods produced in 1989-90 was observed for only one accession (M. truncatula "Cyprus'). New plant re-establishment and seed production was observed in 1990-91 for all five accessions from seed produced in 1989-90 with supplemental irrigation (300 mm) in addition to precipitation. Rapid maturing medics that exhibit breakdown of hardseededness by autumn appear to be well adapted to S Arizona sites receiving as little as 110 mm winter precipitation. If such introductions are to be successful, initial seeding rates >115 pure live seeds/m2 may be necessary to develop a large soil seed bank. -from Authors
• Zhu, T., Mogensen, H., & Smith, S. E. (1993). Quantitative, three-dimensional analysis of alfalfa egg cells in two genotypes: Implications for biparental plastid inheritance. Planta, 190(2), 143-150.
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  Abstract: In alfalfa (Medicago sativa L.), plastids are inherited biparentally. Patterns of plastid transmission vary according to the genotypes involved, but there is a strong bias in favor of male plastid transmission. Previous cytological studies on the male gametophyte of this species have not provided an adequate explanation for the differences in plastid transmission frequencies among genotypes. In the present study, we compared egg cells from genotypes classified as strong or weak plastid transmitters to determine whether plastid transmission strength is correlated with egg cell structure before fertilization. We found that plastids in the mature egg cells of the strong female (genotype 6-4) are significantly larger than in mature eggs of the weak female (genotype CUF-B), and that significantly more plastids are positioned in the apical portion of the mature egg cell of genotype 6-4 than in CUF-B. Immature eggs in the two genotypes show the same pattern as mature eggs with regard to plastid number and polarization. Since only the apical portion of the egg cell/zygote gives rise to the functional embryo, these results indicate that the potential input of female plastids, in terms of plastid size and number, may be an important factor in determining the inheritance patterns of these organelles in alfalfa. © 1993 Springer-Verlag.
• Forsthoefel, N. R., Bohnert, H. J., & Smith, S. E. (1992). Discordant inheritance of mitochondrial and plastid DNA in diverse alfalfa genotypes. Journal of Heredity, 83(5), 342-345.
• Johnson, D. W., & Smith, S. E. (1992). Response to NaCl of alfalfa plants regenerated from non-saline callus cultures. Plant and Soil, 143(2), 311-315.
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  Abstract: Salinity restricts crop productivity in many arid environments. Inadvertent selection for tolerance to osmotic stress may occur under cell or tissue culture conditions and could affect the performance of regenerated plants. The effect of NaCl on forage produced by alfalfa (Medicago sativa L.) plants regenerated from non-saline callus cultures was examined in this study. Plants of Regen-S, which was selected for improved callus growth and regeneration in non-saline cultures, had higher forage weight when grown on SHII medium at NaCl levels up to 100 m M compared to its parental cultivars, Saranac and DuPuits. Five additional original-regenerant plant pairs, each derived from non-saline callus cultures of different alfalfa plants, were evaluated in a solid (soil-like) substrate under saline and non-saline conditions. Weight of forage produced by rooted stem cuttings of regenerated plants was 33% higher at 50 m M NaCl compared to cuttings of explant donor plants. Self progenies from four of five regenerants had higher relative forage weight at 100 m M NaCl (percent of 0 NaCl treatment) than the original plants indicating increased NaCl tolerance. © 1992 Kluwer Academic Publishers.
• Johnson, D. W., Smith, S. E., & Dobrenz, A. K. (1992). Genetic and phenotypic relationships in response to NaCl at different developmental stages in alfalfa. Theoretical and Applied Genetics, 83(6-7), 833-838.
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  PMID: 24202761;Abstract: The perennial forage alfalfa (Medicago sativa L.) may be affected by salinity at all stages of development. Selection for increased seed germination or seedling growth in saline environments has not resulted in improved forage yield under salt stress. The purpose of this study was to determine genetic and phenotypic relationships between plant performance in the presence of NaCl at three developmental stages in alfalfa. Understanding these relationships may improve the efficiency of breeding programs aimed at increasing crop survival and yields in saline environments. Fourteen half-sib families were randomly chosen from both an experimental alfalfa population produced from two cycles of mass selection for improved forage regrowth yield at 80 m M NaCl (A80), as well as from an unselected control population (AC1). In two separate experiments, individual plant performance was measured in these families at seed germination (radicle length at 7 days), and during seedling growth (forage yield at 40 days post-planting) and post-harvest regrowth (forage yield at 67 and 95 days post-planting) in the presence of 0 or 80 m M NaCl. Genetic, phenotypic, and family rank correlation coefficients, and broad-sense and narrow-sense heritability estimates were calculated within each growth stage, NaCl level, and population. Radicle length was not highly correlated with seedling or regrowth forage yield within a population or across NaCl levels. Phenotypic correlations between seedling and regrowth yields were also low. Heritability estimates were higher at 0 NaCl in AC1 between all growth stages, but were greater in A80 at 80 m M NaCl. Genetic correlations between seedling and regrowth yields were all positive. This suggests that selection for forage yield in saline environments at harvests-1,-2, or -3 should not decrease performance at other stages. Genetic correlations between seedling and regrowth yields were higher in A80 than in AC1 at 80 m M NaCl. The results indicate that selection for increased alfalfa forage yield in saline environments at germination may not be optimum. Family selection at germination or during seedling growth may be more effective than individual plant selection at any growth stage in saline environments. The results suggest than selection methods which include each critical growth stage may be required to develop alfalfa cultivars with increased forage yield in saline environments. © 1992 Springer-Verlag.
• Johnson, D. W., Smith, S. E., & Dobrenz, A. K. (1992). Selection for increased forage yield in alfalfa at different NaCl levels. Euphytica, 60(1), 27-35.
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  Abstract: Alfalfa (Medicago sativa L.) forage yield may be reduced by moderate levels of salinity. Increasing forage yield in saline environments through plant breeding could partially ameliorate this problem. However, prior indirect selection either in cell culture, at germination, or during seedling growth has not resulted in agronomically relevant levels of salt tolerance. This study was conducted to determine whether mean forage yield of alfalfa grown in saline environments could be increased. To reduce the number of possible selection schemes, forage yield data for five harvests from 'Sonora' and its parental cultivar 'African' grown in a greenhouse and irrigated with 0, 30, 60, or 80 mM NaCl were used to simulate one cycle of selection at each NaCl environment. Greatest gains in forage yield were expected under non-saline conditions with decreased gains under saline conditions. Selection based on yield in regrowth harvests was also predicted to be more efficient than that based on seedling harvest. Experimental populations were developed from Sonora and African at each NaCl level using phenotypic selection for increased mean forage yield for harvests 3 to 5. After each of two cycles of selection, forage yield from selected, control (plants selected randomly under non-saline conditions), and parental populations was evaluated at 0, 30, 60, and 80 mM NaCl. Gains in forage yield were observed in African when the selection and evaluation environments were the same, but in Sonora this was observed only at 0 NaCl. Selection at 0 NaCl did not increase forage yield at 60 or 80 mM NaCl in either germplasm source. This suggests that selection for increased forage yield may be successful at low to moderate NaCl levels in germplasm with ample variation for yield when grown in saline environments, while selection for increased forage yield in non-saline conditions may be ineffective. © 1992 Kluwer Academic Publishers.
• Zhu, T., Mogensen, H. L., & Smith, S. E. (1992). Heritable paternal cytoplamsic organelles in alfalfa sperm cells: Ultrastructural reconstruction and quantitative cytology. European Journal of Cell Biology, 59(1), 211-218.
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  PMID: 1468441;Abstract: Sperm cells within pollen grains and pollen tubes of alfalfa (Medicago sativa L.) were observed at the ultrastructural level, and their plastid DNA was detected by DAPI (4,6-diamidino-2-phenylindole) staining. One sperm pair within the pollen grain and three sperm pairs within pollen tubes were reconstructed in three-dimensions from serial ultrathin sections. The two sperm cells are linked by cytoplasmic bridges in both pollen grains and tubes, and the vegetative nucleus is closely associated with the sperm cells within the pollen tube. The number of plastids and plastid nucleoids (DNA aggregates) in the sperm cell pair, collectively, is not significantly different from that in the generative cell; however, over 60% of the sperm cell plastids contain no DNA detectable with DAPI The mean number of mitochondria in sperm cells is reduced from that in the generative cell (from 54 to 17), which suggests that paternal mitochondrial inheritance probably does not occur in the genotype investigated. Sperm cells of a pair may vary in their shape within the pollen grain and tube, but the number of plastids and mitochondria is not significantly different between the sperm cells. Therefore, heterospermy is not a factor determining cytoplasmic inheritance patterns in this species.
• Shi, L., Mogensen, H. L., Zhu, T., & Smith, S. E. (1991). Dynamics of nuclear pore density and distribution patterns within developing pollen: Implications for a functional relationship between the vegetative nucleus and the generative cell. Journal of Cell Science, 99(1), 115-120.
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  Abstract: Quantitative transmission electron microscopy was used to study pore density (mean pore number±standard deviation/nuclear envelope area) on developing pollen nuclei of alfalfa. We found that pore density is essentially uniform around the vegetative nucleus (VN) at an early developmental stage (29±6 pores μm-2), but later, when the VN forms a close physical association with the generative cell (GC), nuclear pore density is 69% higher on the surface of the VN facing the GC (27±12 pores μm-2) compared to the surface away from the GC (16±9 pores μm-2). The surface area of the VN does not change significantly during the stages of this study. Pore density is nearly equal on vegetative and generative nuclei in young pollen, but at pollen maturity the VN has a mean pore density 3.5 times greater than that of the generative nucleus. Our results are consistent with those of other studies comparing pore densities on developing and mature pollen nuclei. However, this is the first study, to our knowledge, that has followed vegetative nuclear pore density and distribution as it relates to the formation of a close physical association between the VN and the GC. Taken together with biochemical studies on RNA and protein synthesis during pollen development, and studies on nuclear pore function, these results support the notion that even though mean pollen nuclear activity may decrease during pollen maturation, the potential for nucleocytoplasmic exchange is not diminished appreciably in the area of the VN-GC association. This suggests that there is a direct functional relationship between the VN and the GC, and that gene expression may be not only temporally but also spatially separated within the VN during pollen development.
• Shi, L., Zhu, T., Mogensen, H. L., & Smith, S. E. (1991). Paternal plastid inheritance in alfalfa: Plastid nucleoid number within generative cells correlates poorly with plastid number and male plastid transmission strength. Current Genetics, 19(5), 399-401.
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  Abstract: A previous study on alfalfa determined that the number of plastids/generative cell does not necessarily correlate with male plastid transmission strength in a given genotype. The objectives of the present study were to learn (1) whether plastid nucleoid number/generative cell is comparable to the number of plastids/generative cell, and (2) whether plastid nucleoid number/generative cell correlates with known male plastid transmission behavior in three alfalfa genotypes. Our results, which were based upon 150 generative cells examined by DAPI/epifluorescence microscopy, indicate that the mean plastid nucleoid number/generative cell is much less than the mean number of plastids/generative cell in genotype 7W (60 nucleoids/264 plastids) and genotype 301 (54 nucleoids/165 plastids). In genotype MS-5, mean plastid nucleoid number/generative cell (45) is similar to the mean number of plastids/generative cell (65). The significantly fewer plastid nucleoids/generative cell in MS-5, compared to that of 7W and 301, correlates positively with the relatively poor male plastid transmission strength of this genotype. However, the difference between the mean number of plastid nucleoids/generative cell in 7W and 301 is not significant, yet 301 is a much stronger transmitter of male plastids than is 7W.
• Zhu, T., Mogensen, H. L., & Smith, S. E. (1991). Quantitative cytology of the alfalfa generative cell and its relation to male plastid inheritance patterns in three genotypes. Theoretical and Applied Genetics, 81(1), 21-26.
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  PMID: 24221154;Abstract: Studies utilizing restriction analysis of plastid DNA, as well as those employing chlorophyll-deficient mutants, have shown a high frequency of paternal plastid transmission in alfalfa. Recent research has also shown that plastid inheritance patterns among alfalfa genotypes and are under genetic control. In a previous study we were unable to detect any correlations between qualitative, three-dimensional ultrastructure of generative cells and male plastid transmission strength in certain genotypes. In the present study we used serial ultrathin sectioning, computerized reconstruction and quantitation, and stereology to further analyze generative cells within mature pollen. Measurements included volumes and surface areas of cells, nuclei, and organelles, as well as organelle number and distribution. Three genotypes were investigated, one that is a strong transmitter of male plastids (genotype 301), one that is a weaker transmitter of male plastids (genotype 7W), and a third that is an even weaker male plastid transmitter (genotype MS-5). Our results show that genotype MS-5 has significantly fewer plastids/generative cell than either of the other genotypes, which may account for it being a relatively poor transmitter of male plastids. However, plastid number does not explain known differences in male plastid inheritance between genotypes 301 and 7W, since plastid number does not differ significantly between these two genotypes. Regarding the other features of generative cells measured in this study, no consistent correlations were found that might account for differences in male plastid inheritance patterns between genotypes. Plastid distribution is equal in each end of the spindle-shaped generative cell in all genotypes studied. Similar relative results were found with regard to mitochondria within generative cells; however, comparative genetic data are not available on mitochondrial transmission patterns in alfalfa genotypes. © 1991 Springer-Verlag.
• Zhu, T., Mogensen, H. L., & Smith, S. E. (1990). Generative cell composition and its relation to male plastid inheritance patterns in Medicago sativa. Protoplasma, 158(1-2), 66-72.
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  Abstract: Genetic studies have recently shown that plastids are inherited biparentally in alfalfa; yet most crosses produce high frequencies of progenies containing only paternal plastids, and certain genotypes have been characterized as relatively strong or weak transmitters of male plastids. The objective of the present study was to determine whether the structure of generative cells differs among genotypes known to differ in male plastid transmission pattern. Using the techniques of serial ultrathin sectioning and three-dimensional reconstruction, we found that mature generative cells of the genotypes investigated have basically similar morphology, and contain numerous plastids in each end of the spindle shaped cell. Since the morphological variation that does occur is as great within a genotype as it is between genotypes, it does not appear that generative cell structure can be used to predict male plastid transmission behavior in a particular genotype. The number of mitochondria in generative cells, which is much less than that of plastids, varies considerably among genotypes. However, comparable genetic studies between genotypes are not yet available on male mitochondrial inheritance in alfalfa. © 1990 Springer-Verlag.
• Smith, S. E. (1989). Influence of parental genotype on plastid inheritance in Medicago sativa. Journal of Heredity, 80(3), 214-217.
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  PMID: 2732452;Abstract: Research using chlorophyll-deficient mutants has shown that plastids are inherited biparentally in Medicago sativa L. (alfalfa). Variation in plastid transmission behavior was observed among crosses in earlier studies, but it was not determined whether this variation was under genetic control. In my research, genetic analyses of the frequencies of normal (G), chlorophyll-deficient (CD), and sectored (G and CD) progenies produced from G x CD crosses demonstrated that plastid inheritance patterns in alfalfa are influenced by both maternal and paternal genotypes. A strong paternal bias in plastid transmission existed in the majority of crosses despite the potential developmental disadvantages associated with paternally contributed CD plastids. The high frequencies of uniparental progenies suggest that genetic control of plastid inheritance in alfalfa may be exerted through effects on the number and distribution of maternal and paternal plastids early in embryo development. © 1989 The American Genetic Association.
• Smith, S. E., Meiners, M., Putzar, N., & Dobrenz, A. K. (1989). Potential use of measurements of callus and male gametophyte NaCl tolerance in lucerne breeding. Euphytica, 43(3), 245-251.
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  Abstract: Relationships between whole-plant and germination NaCl tolerance and two in vitro measures of NaCl tolerance were evaluated in lucerne (Medicago sativa L.). No significant correlations were observed between relative NaCl tolerance of non-regenerating callus cultures, herbage regrowth, seed or pollen germination, and pollen tube growth. Simulated selection using indirect measures of NaCl tolerance produced small expected gains in relative NaCl tolerance during herbage regrowth and seed germination. These gains were less than 30% of those expected with direct selection for regrowth or germination tolerance. Selection based on the apparent NaCl tolerance of callus tissue or male gamephytes would appear unproductive. Direct selection for NaCl tolerance both at germination and during mature plant regrowth would appear to be necessary to rapidly develop lucerne populations with field-relevant levels of tolerance to NaCl stress. © 1989 Kluwer Academic Publishers.
• Fairbanks, D. J., Smith, S. E., & Brown, J. K. (1988). Inheritance of large mitochondrial RNA's in alfalfa. Theoretical and Applied Genetics, 76(4), 619-622.
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  PMID: 24232285;Abstract: Several large RNA molecules that migrated to electrophoretic positions ranging from 1.7-10 kb were observed in preparation of alfalfa (Medicago sativa) mitochondria. F1 progenies inherited the RNA's from both maternal and paternal parents (Fig. 1). Treatment of intact mitochondria with RNase A failed to remove the RNA's, indicating that they were contained within an RNase impermeable compartment. Further purification of mitochondria in linear sucrose gradients failed to separate the RNA's from mitochondria. Transmission electron microscopic examination of sucrose gradient purified mitochondria revealed that mitochondria were free of contamination by virus-like particles, indicating that the RNA's were contained within the mitochondrion. Biparental inheritance of large mitochondrial RNA's in alfalfa provides evidence that mitochondria are inherited biparentally in this species. © 1988 Springer-Verlag.
• Lee, D. J., Blake, T. K., & Smith, S. E. (1988). Biparental inheritance of chloroplast DNA and the existence of heteroplasmic cells in alfalfa. Theoretical and Applied Genetics, 76(4), 545-549.
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  PMID: 24232273;Abstract: Mapping of chloroplast DNA (ctDNA) restriction fragment patterns from a chlorophyll deficient mutant and two phenotypically normal alfalfa genotypes (Medicago sativa L.) has demonstrated the existence of a distinct ctDNA genotype from each source. These unique restriction fragment patterns were utilized to identify maternal or paternal origin of ctDNA in hybrid plants from crosses involving the normal alfalfa genotypes as females and the yellow-green chlorophyll deficient sectors as males. Progeny from these crosses expressing the yellow-green sectored phenotypes contained paternal ctDNA in the chlorophyll deficient sectors and maternal ctDNA in the normal sectors, confirming biparental plastid inheritance. The existence of mixed cells containing both mutant and normal plastids at various stages of sorting-out was observed by transmission electron microscopy of mesophyll cells in mosaic tissue from hybrid plants. This observation verified the biparental transmission of plastids in alfalfa. © 1988 Springer-Verlag.
• Smith, S. E., Bingham, E. T., & Fulton, R. W. (1986). Transmission of chlorophyll deficiencies in Medicago sativa: Evidence for biparental inheritance of plastids. Journal of Heredity, 77(1), 35-38.
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  Abstract: Developmental patterns and transmission of two chlorophyll deficiencies were studied in tetraploid Medicago sativa L (alfalfa). Both chlorophyll deficiencies originally appeared as sectors within otherwise normal (green) tissue. One of the deficiencies arose in tissue culture and had yellow-light green sectors in normal leaves and stems. The other variant was discovered in a breeding population and exhibited albino sectoring in shoot tissues. Neither chlorophyll deficiency was sap-or graft-transmitted, indicating that virus infection was not responsible for the irregularities in coloration. Developmental patterns in sectored plants were characteristic of the sorting-out of normal and abnormal plastids. Significant reciprocal differences in rates of transmission were observed for both traits in crosses of chlorophyll-deficient and normal plants. Transmission of both chlorophyll deficiencies was higher through the pollen than through the egg. All developmental and genetic evidence strongly suggests that both chlorophyll deficiencies represent plastid mutations, and that plastids are inherited biparentally in M. sativa. © 1986, American Genetic Association.

Presentations

• Smith, S. E. (2013, March). Predicting Pine Distribution at High Elevations in the Madrean Archipelago and Sierra Madre Occidental.. University of Arizona Herbarium Seminar Series.

Poster Presentations

• Papuga, S. A., Rotunno, M., Schaller, A., Pope, A., Archer, S. R., & Smith, S. E. (2016, Spring). Understanding source water dynamics for a deep-rooted desert shrub using stable water isotopes: an experimental two-layer approach. UA Earth Week Student Symposium.
• Rotunno, M. A., Papuga, S. A., Archer, S. R., Schaller, A., Pope, A. J., & Smith, S. E. (2016, April). Understanding source water dynamics for a deep-rooted desert shrub using stable water isotopes: an experimental two-layer approach. Earth Week. University of Arizona.

Others

• Soto, J. R., Smith, S. E., Ruyle, G. B., Mcclaran, M. P., Lopez Hoffman, L., Lien, A., Howery, L. D., Gornish, E., Fehmi, J. S., & Archer, S. R. (2021, May). Annual Report, Ecology, Management and Restoration of Rangelands. USDA NIFA Hatch Project ARZT-1361610-H12-223, 11 pp..
• Soto, J. R., Smith, S. E., Ruyle, G. B., Mcclaran, M. P., Lopez Hoffman, L., Lien, A., Howery, L. D., Gornish, E., Fehmi, J. S., & Archer, S. R. (2021, May). Annual Report, Ecology, Management and Restoration of Rangelands. USDA NIFA Report.
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  Hatch Project Annual Report ARZT-1361610-H12-223, 11 pp.
• Soto, J. R., Soto, J. R., Smith, S. E., Smith, S. E., Ruyle, G. B., Ruyle, G. B., Mcclaran, M. P., Mcclaran, M. P., Lopez Hoffman, L., Lopez Hoffman, L., Howery, L. D., Howery, L. D., Gornish, E., Gornish, E., Fehmi, J. S., Fehmi, J. S., Archer, S. R., & Archer, S. R. (2020, May). Annual Report, Ecology, Management and Restoration of Rangelands. USDA NIFA ARZT-1361610-H12-223 REEPort.
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  Hatch Project Annual Report, 14 pp.