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Central Asia, particularly Kazakhstan, supports a rich concentration of wild alfalfa (Medicago sativa L.) relatives. Because tetraploid wild alfalfa freely crosses with domesticated alfalfa, they are important genetic resources. When identifying in situ populations to conserve, contamination of wild populations with domesticated alleles is an important consideration. We evaluated population structure and introgression between six wild populations of M. sativa nothossp, varia collected in northwestern Kazakhstan and five traditional Russian cultivars historically grown in the same region using two amplified fragment length polymorphism primer pairs and six simple sequence repeat loci. We found no difference between the Russian cultivars and wild populations for number of alleles or percentage polymorphic loci; however, gene diversity was less in the wild than in the cultivated populations. Cluster analysis and principle component analysis showed clear separation between wild and cultivated populations. Genetic differentiation among the cultivars was less than among the wild populations. Using a Bayesian approach, we found limited evidence of admixture among the wild and cultivated forms, although more admixture was evident in wild populations collected in less-remote areas. On the basis of marker data, we concluded that three of the six wild populations stood out as candidates for in situ conservation given their uniqueness and lack of admixture with cultivated forms.

The amount of genetic variation within species and populations and the distribution of genetic diversity (GD) among populations are important to breeders and biologists. The objective of this study was to assess GD on the basis of isozymes in 15 wild red clover (Trifolium pratense L.) populations collected in the Caucasus Mountains, Russia. Isozymes assayed were esterase, β-glucosidase, phosphoglucomutase, peroxidase, diaphorase, phosphoglucoisomerase, and superoxide dismutase. Ten isozyme loci with 26 alleles were detected. Ninety percent of the loci were polymorphic in at least one population. Percent polymorphic loci within populations ranged between 50 and 90%. At the species level, the number of alleles per polymorphic locus was 2.89 and effective number of alleles per locus was 1.84. Within-population averages were 2.75 and 1.70, respectively. Genetic diversity was 0.353 at the species level and the mean value for the populations was 0.323. Some of the populations such as PI 604728 and PI 604735 were unique at the at the isozyme level. The other 13 accessions could be consolidated into one accession. Diversity measurements indicated that this species has a high level of variability that resides mostly within populations. Gene flow expectations based on predictions using topographic maps developed using interpolated digital and climatic surfaces coincided with gene flow estimates obtained using isozymes. This supports the use of GIS tools and remotely sensed data to develop maps that help germplasm collection and post-collection efforts to understand patterns of GD in collected germplasm., RED CLOVER is one of the most important forage species in the USA and the world. It is a short-lived perennial diploid species that is able to grow in a [...]

Cyanogenesis, the production of hydrocyanic acid, is a trait in white clover (Trifolium repens L.) controlled by alleles at two unlinked loci, Ac and Li. The objectives of this study were (i) to determine the proportion of cyanogenic plants in the accessions of the U.S. white clover germplasm collection, (ii) to determine how representative the core subset was of the entire collection for cyanogenesis, and (iii) to determine the relationship of cyanogenesis, in accessions collected in situ, to collection site and climate. Twenty plants from each of 548 white clover accessions were grown in the greenhouse from 1991 to 1993. Two to three leaves per plant were harvested and the presence or absence of hydrocyanic acid was determined by the picric acid test. The U.S. germplasm collection was predominantly acyanogenic with a third of the plants evaluated being cyanogenic. Accessions with the most cyanogenic plants were collected in Morocco, Spain, Portugal, France, and Turkey while the least cyanogenic plants were collected in China, Romania, Russia, Kazakhstan, Croatia, Bosnia-Herzegovina, and Slovenia. Accessions collected in Morocco, Portugal, and Spain had the greatest intensity of cyanogenic reaction. Geographic stratification with random sampling was an effective method of developing a core subset, as the white clover core subset was representative of the entire collection for total cyanogenesis and distribution of cyanogenic plants. Cyanogenic frequency was greater in accessions collected at low altitudes and at sites with high winter temperatures, lower summer precipitation, greater spring cloudiness (% sunshine), and less snow cover. Latitude of collection was not associated with cyanogenic frequency in white clover.

Societal Impact Statement: Crop wild relatives—wild species closely related to cultivated plants—are valuable genetic resources for crop improvement, but gaps in knowledge constrain their conservation and limit their further use. We develop new information on the distributions, potential breeding value, and conservation status of the 16 known wild relatives of cultivated pumpkins, squashes, zucchini, and gourds (Cucurbita L.). The taxa occur from the central USA to Central America, plus two South American species, with the greatest richness in central Mexico and the western borderlands between Mexico and the USA. We determine the majority of species are of medium priority for conservation, both with regard to collecting for ex situ maintenance, and for enhanced habitat protection. SummaryCrop wild relatives are valuable genetic resources for crop improvement. Knowledge gaps, including with regard to taxonomy, distributions, and characterization for traits of interest constrain their use in plant breeding. These deficiencies also affect conservation planning, both with regard to in situ habitat protection, and further collection of novel diversity for ex situ maintenance.Here we model the potential ranges of all 16 known wild cucurbit taxa (Cucurbita L.), use ecogeographic information to infer their potential adaptations to abiotic stresses, and assess their ex situ and in situ conservation status.The taxa occur from the central USA to Central America, plus two South American species. Predicted taxon richness was highest in central Mexico and in the western borderlands between Mexico and the USA. We find substantial ecogeographic variation both across taxa and among populations within taxa, with regard to low temperatures, high and low precipitation, and other adaptations of potential interest for crop breeding.We categorize 13 of the taxa medium priority for further conservation as a combination of the ex situ and in situ assessments, two low priority, and one sufficiently conserved. Further action across the distributions of the taxa, with emphasis on taxonomic richness hotspots, is needed to comprehensively conserve wild Cucurbita populations. [ABSTRACT FROM AUTHOR]

Without committing significant resources in the decision-making process, curators are challenged to identify among newly collected germplasm, exceptional accessions that merit inclusion in ex situ collections. The objectives of this paper were to illustrate how geographic information can be used to infer (i) site uniqueness relative to other sites sampled, (ii) the likelihood that an accession reflects adaptation to the site, and (iii) uniqueness of a given accession relative to other accessions of the same taxon collected. Forage legume germplasm was collected from the western Caucasus Mountains in southern Russia in 1995. Prior to the trip, a database was developed from geographic information system software that included data from Russian maps, orbital satellite imagery, remotely sensed elevation data, and long-term climate data from weather stations. Data were collected characterizing the collection sites. A map was developed that partitioned the collection area into standard landscape units from the GIS-derived climate data. The cross-classification map was used to assess collection coverage and identify sites that had similar ecogeographic characteristics. Germplasm was collected from 41% of the possible moisture and temperature zone combinations. Site redundancy was also identified. Local passport data, GIS-derived data and the cross-classification map were used to identify accessions of Trifolium pratense L. adapted to acid soil by inferring the influence of micro evolutionary forces such as selection and gene flow that could lead to geographic differentiation. Of 36 accessions, six met the test of being collected from undisturbed sites with acidic soils, being the sole representatives of unique climate classes and having been isolated from other T. pratense accessions. The post-collection analysis provided a cost-effective way of determining the accessions that warranted inclusion into the NPGS T. pratense germplasm collection., Curators are responsible for developing ex situ germplasm collections that serve the dual purpose of providing useful breeding material in the present and conserving crop gene pools for the future [...]

A common strategy for sampling intraspecific genetic diversity is to maximize the sampling of geographically distinct populations. The objective of this study was to illustrate how geographic information coupled with geographic information systems (GIS) analysis can provide a new level of precision for establishing frameworks for sampling germplasm occurring in ecogeographically diverse sites. An exploration to collect forage germplasm in the western Caucasus Mountains in southern Russia, carried out jointly by the National Plant Germplasm System and the N.I. Vavilov Institute of Plant Industry in 1995, was used as a case study. The development of a GIS database and resulting map products and how these products were used to guide the sampling of geographically-distinct areas is discussed. Information sources included Russian maps, orbital satellite imagery, remotely-sensed elevation data and long-term climate data from weather stations. A GIS database was developed and used to produce the following maps: soil classification, roads and trails, vegetation, and topography. Climate modeling techniques were used to develop maps reflecting climate zones. During the collecting trip, the strengths and weaknesses of the various map products became evident. The satellite imagery could be effectively used to identify potential meadow sites, but did not reflect more recent anthropogenic disturbance. Soil maps comprised of original Russian agricultural soil maps failed to reflect the extreme heterogeneity of soil types. Assessment of map-based and site-specific geographic features during the collection trip provided collectors with an increased understanding of how the physical features of the collection landscape may have influenced the geographic differentiation of 75% of the germplasm accessions collected., The geographic differentiation of plant populations reflects the dynamics of gene flow and natural selection, which can be strongly influenced by the environment (Epperson, 1990; Slatkin, 1987; Spieth, 1979; Bradshaw, [...]

Drought is a major environmental factor hampering alfalfa productivity worldwide. Gene banks provide an array of trait diversity, frequently consisting of specific seed collection projects that focused on acquiring germplasm adapted to specific traits such as drought tolerance. These subsets provide a logical starting point to identify useful breeding resources. In the present study, we investigated the genetic diversity and evaluated 18 agronomic, physiological and quality traits associated with drought tolerance in a subset of 198 alfalfa accessions collected for their potential drought resistance. Significant differences were found among accessions for most of the traits evaluated. Water deficit significantly decreased biomass dry yield by 61.9% compared with well-watered control. A positive correlation was found between relative water content (RWC) and drought susceptible index, while negative correlations were found between RWC and leaf senescence (LS), and between RWC and canopy temperature (CT). Alfalfa accessions with high RWC showed relative lower yield reduction, cooler CT and delayed LS. Genetic variation for forage quality was also investigated and the correlation between agronomic and quality traits was analyzed. Biomass yield under drought was negatively correlated with total protein, relative feed value and relative forage quality, suggesting that the efforts to improve yield under drought tend to negatively affect forage quality. Therefore, maintaining forage quality should be considered for breeding alfalfa with drought resistance. Alfalfa accessions with high drought resistance scores and minimum loss of quality were identified in this study and can be used as genetic resources for developing alfalfa varieties with improved drought resistance and water use efficiency while maintaining forage quality. [ABSTRACT FROM AUTHOR]

Contracted commercial beekeeping operations provide an essential pollination service to many agricultural systems worldwide. Increased use of genetically engineered crops in agriculture has raised concerns over pollinator-mediated gene flow between transgenic and conventional agricultural varieties. This study evaluated whether contracted migratory beekeeping practices influence transgenic pollen flow among spatially isolated alfalfa fields. Twelve honey bee (Apis mellifera L.) colonies were permitted to forage on transgenic alfalfa blossoms for 1 wk in Touchet, WA. The hives were then transported 112 km to caged conventional alfalfa plots following one and two nights of isolation (8 and 32 h, respectively) from the transgenic source. Alfalfa seed harvested from the conventional plots was assessed for the presence of the transgene using a new seedling germination assay. We found that 8 h of isolation from a transgenic alfalfa source virtually eliminated the incidence of cross-pollination between the two varieties. [ABSTRACT FROM AUTHOR]

Economically, legumes (Fabaceae) represent the second most important family of crop plants after the grass family, Poaceae. Grain legumes account for 27% of world crop production and provide 33% of the dietary protein consumed by humans, while pasture and forage legumes provide vital part of animal feed. Fabaceae, the third largest family of flowering plants, has traditionally been divided into the following three subfamilies: Caesalpinioideae, Mimosoideae, and Papilionoideae, all together with 800 genera and 20,000 species. The latter subfamily contains most of the major cultivated food and feed crops. Among the grain legumes are some of mankind's earliest crop plants, whose domestication parallelled that of cereals: Soybean in China; faba bean, lentil, chickpea and pea in the Fertile Crescent of the Near East; cowpeas and bambara groundnut in Africa; soybean and mungbeans in East Asia; pigeonpea and the grams in South Asia; and common bean, lima bean, scarlet runner bean, tepary bean and lupin in Central and South America. The importance of legumes is evidenced by their high representation inex situgermplasm collections, with more than 1,000,000 accessions worldwide. A detailed knowledge of the phylogenetic relationships of the Fabaceae is essential for understanding the origin and diversification of this economically and ecologically important family of angiosperms. This review aims to combine the phylogenetic and genetic diversity approaches to better illustrate the origin, domestication history and preserved germplasm of major legume crops from 13 genera of six tribes and to indicate further potential both for science and agriculture. [ABSTRACT FROM PUBLISHER]

A standard conservation strategy for plant genetic resources integrates in situ (on-farm or wild) and ex situ (gene or field bank) approaches. Gene bank managers collect ex situ accessions that represent a comprehensive snap shot of the genetic diversity of in situ populations at a given time and place. Although simple in theory, achieving complementary in situ and ex situ holdings is challenging. Using Trifolium thompsonii as a model insect-pollinated herbaceous perennial species, we used AFLP markers to compare genetic diversity and structure of ex situ accessions collected at two time periods (1995, 2004) from four locations, with their corresponding in situ populations sampled in 2009. Our goal was to assess the complementarity of the two approaches. We examined how gene flow, selection and genetic drift contributed to population change. Across locations, we found no difference in diversity between ex situ and in situ samples. One population showed a decline in genetic diversity over the 15 years studied. Population genetic differentiation among the four locations was significant, but weak. Association tests suggested infrequent, long distance gene flow. Selection and drift occurred, but differences due to spatial effects were three times as strong as differences attributed to temporal effects, and suggested recollection efforts could occur at intervals greater than fifteen years. An effective collecting strategy for insect pollinated herbaceous perennial species was to sample >150 plants, equalize maternal contribution, and sample along random transects with sufficient space between plants to minimize intrafamilial sampling. Quantifying genetic change between ex situ and in situ accessions allows genetic resource managers to validate ex situ collecting and maintenance protocols, develop appropriate recollection intervals, and provide an early detection mechanism for identifying problematic conditions that can be addressed to prevent further decline in vulnerable in situ populations. [ABSTRACT FROM AUTHOR]