1a. Objectives (from AD-416)
Strategically expand the genetic diversity in genebank collections and improve associated information for priority vegetable, sorghum, peanut, subtropical/tropical legume, and warm-season grass genetic resources. Conserve and regenerate priority vegetable, sorghum, peanut, subtropical/tropical legume, new crop, and warm-season grass genetic resources efficiently and effectively, and distribute pathogen-tested samples and associated information worldwide. Strategically characterize (“genotype”) and evaluate (“phenotype”) priority vegetable, sorghum, peanut, subtropical/tropical legume, and warm-season grass genetic resources for molecular markers, morphological descriptors, and key agronomic or horticultural traits such as biochemical content and product quality. Conserve, regenerate, and distribute germplasm of specialty crops, current or potential bioenergy crops (e.g., sweet sorghum, switch grass, and Miscanthus), and new genetic stocks generated by genomic research (e.g., assocition mapping projects) with sorghum and other crops.
1b. Approach (from AD-416)
Acquire samples of native warm-season grasses, bioenergy crops, subtropical legumes, Ipomoea species, chile pepper, and annual clovers to fill current gaps in NPGS collections. Survey existing holdings of sorghum genetic stocks, identify material that would fill gaps in NPGS collections, and begin acquiring and characterizing them. Conserve and distribute genomic research genetic stocks including association mapping populations of sorghum and other crops. Regenerate, conserve, and distribute more than 88,000 accessions of specialty crops, bioenergy crops, and other priority genetic resources and associated information. Increase the number of sweetpotato and warm-season grass clonal accessions maintained in tissue culture. Increase to 95 percent the proportion of the collection backed up at second sites. Develop superior regeneration methods for seed and clonally-propagated crops. Assay stored genetic resources for vigor, viability, and health. Distribute on request accessions and information that meet the specific needs of researchers and breeders. Develop and apply new genetic markers for phylogenetic and genetic diversity analyses of priority crops. Update and apply phenotypic descriptors for vegetables, peanuts, warm-season grasses, and subtropical/tropical legumes. Develop, enhance, and/or apply high performance liquid chromatography (HPLC) procedures for analyzing variation in flavonoids, antioxidants, capsaicin, and other key phytochemicals in accessions. Incorporate characterization, phenotypic, and biochemical data into GRIN and/or other databases.
3. Progress Report
A total of 90,668 accessions of 1,546 plant species were maintained in the Griffin plant genetic resources collection. Over 87.9% of accessions were available for distribution to users and over 96.3% were backed up for security at a second location. Bulk seed samples for 62,524 accessions were maintained at -18 C for long-term storage with seed of the remaining accessions stored at 4 C. A total of 40,449 seed and clonal accessions in 899 separate orders were distributed upon request to scientists and educators in 50 U.S. states and 38 foreign countries. Acquisitions made to the collection included 354 sorghum, 125 peanut, 70 annual clover, 68 warm-season grasses, and 22 vegetable accessions. A plant collection trip was conducted in northern Florida for native switchgrass germplasm. Seed regenerations and characterization were conducted on 275 peanut, 103 warm-season grass, 70 pepper, 346 legume, new, and misc. crop, 42 annual clover, and 8 cucurbit accessions. New regeneration techniques were developed for Hibiscus and Bituminaria species. Over 300 pepper accessions were grown in the field for characterization and recording of digital images. Digital images of cowpea, sorghum, pepper, and warm-season grass accessions, and pepper root rot and watermelon root knot nematode data were added to the Germplasm Resources Information Network (GRIN). Long-term maintenance of 543 wild peanut and 410 warm-season grass accessions was continued in the greenhouse. Over 30 warm-season grass accessions and 750 sweetpotato accessions were maintained in tissue culture with eight replications of each sweetpotato clone. Virus screening was completed on the sweetpotato collection for sweetpotato leaf curl virus. Germination testing has been completed for 60,207 accessions (over 67% of collection) since 2002. A genotyping technique was developed to detect high oleic acid peanuts and will be useful in evaluating segregating populations to identify progeny with the desirable high oleic acid trait. Molecular analysis and ploidy level determinations are underway for newly acquired switchgrass germplasm from Florida. Basic descriptors were collected on the entire U.S. bamboo collection. The oil content was determined for the entire U.S. castor bean (over 1,000 accessions) and okra (over 1,200 accessions) collections and the U.S. sesame collection is currently being evaluated for oil content. Fifty castor bean accessions are being grown in the field to verify oil content and determine relationships with fatty acid composition. Okra accessions varying in oil content will be evaluated for fatty acid composition. In collaboration with other ARS scientists in Dawson, GA, the peanut mini-core collection was grown in the field for morphological evaluation, is being biochemically analyzed in the lab, and is being genotyped with 84 genetic markers. In collaboration with Kansas State University scientists, association analysis will be conducted to identify association of genetic markers with useful peanut traits.
1. Oil Content in Seed of Okra species. Okra (Abelmoschus spp.) is an oil seed crop that is known to produce oil yields with chemical properties similar to those of cotton seed. ARS researchers at Griffin, GA evaluated more than 1,200 accessions of various okra species for total oil content using nuclear magnetic resonance (NMR). Data indicated that total oil content varied from approximately 4% to >21% and that it was loosely correlated with seed weight. This information will enable researchers to select okra accessions with potential for use as an oil seed crop.
2. Oil Content of the U.S. Castor Bean Collection. Oil content for biodiesel production among the castor bean accessions in the U.S. collection is unknown. ARS researchers at Griffin, GA, found significant variation in oil content (ranging from 37 to 61%) in 1,033 castor bean accessions. Selected castor bean accessions with high oil content can now be used in variety development for use as a biodiesel crop.
3. Improvement of the Switchgrass Germplasm Collection. Evaluation of switchgrass accessions is needed in order to provide well characterized, available and viable material to scientists for use in bioenergy feedstock development. Newly collected switchgrass accessions were tested for germination, regenerated, characterized genotypically using simple sequence repeat (SSR) markers, and ploidy levels determined by ARS researchers at Griffin, GA. This effort will provide well characterized lowland switchgrass germplasm to plant breeders for incorporation into bioenergy feedstock development programs furthering the endeavor towards U.S. energy independence.
4. Capsaicin and Capsiate in Chile Pepper species. The sensory attributes (chemical composition) of vegetables can be an important factor in determining consumer acceptance and demand. ARS researchers at Griffin, GA, investigated the occurrence and concentration of capsaicin and capsiate in Capsicum spp. Capsaicin confers the pungency (heat) associated with hot peppers and capsiate is a related compound. The levels of capsaicin and capsiate ranged from 0 (not present) to >1500 ug and >600 ug/g FW, respectively. Capsiate was present in most of the tested chile pepper accessions. This information will be of benefit to those developing pepper lines or varieties enhanced for either of these compounds.
5. Genotyping Assay Developed for High Oleic Acid Peanuts. ARS researchers in Griffin, GA, developed a genotyping assay using a real-time polymerase chain reaction to detect alleles relating to the high oleic acid trait in peanuts. This assay enables breeders to test seed or leaf tissue in initial crosses without using chemical analysis of ground up seeds. Development of this rapid assay will help identify key genotypes linked to important agronomic traits, improve breeding efficiency by eliminating undesirable plants, and expedite the process of developing improved peanut cultivars by decreasing the time and effort to characterize all of the generated progeny.
6. Techniques Developed to Regenerate Legume Species. Optimum regeneration techniques are unknown for several legume species. ARS researchers at Griffin, GA developed improved regeneration techniques for two legume species. Twelve photoperiod sensitive Hibiscus sabdariffa accessions were successfully regenerated in a greenhouse during the offseason (November – June). Six perennial Bituminaria bituminosa accessions overwintered and produced quality fruits and seed during the second year of growth. Quality seed of these legumes are now available for scientists to use in their research projects.
7. Fatty Acid Variability in Lablab purpureus. Little information is available regarding fatty acid variability in the U.S. Lablab purpureus collection. Significant variation for several fatty acids was found in seven Lablab purpureus accessions by ARS researchers in Griffin, GA. These accessions can now be used by breeders and scientists in the development of new products containing these fatty acids.
8. Biofuel Potential of Sunn Hemp Accessions. Cellulosic ethanol is expected to play a large role in biofuels, however cellulose and biomass variation is unknown among the U.S. sunn hemp (Crotalaria juncea) collection. Glucose is a primary constituent in cellulose and was found to vary among these 16 sunn hemp accessions. ARS researchers at Griffin, GA, also found significant variation accessions for biomass, apical dominance, branching, open flowers, plant height, earliness, and seed production. Several sunn hemp accessions were identified as parental species for use in breeding programs for cultivar development.
Mckinney, J.T., Nay, L.M., Dekoeyer, D., Reed, G.H., Wall, M., Palais, R., Jarret, R.L., Wittner, C. 2010. Mutation Scanning and Genotyping in Plants by High Resolution DNA Melting. Handbook of Plant Mutation Screening. pp 149-163.