1. Acquisition of germplasm. Explorations were focused on collecting germplasm to fill in gaps in the collections, especially in the secondary and tertiary gene pools consisting of wild relatives, which are the main sources of genes for biotic and abiotic stresses and extended adaptation. The National Clonal Germplasm Repository (NCGR), Davis plant explorations during 2009 resulted in acquisition of 86 accessions representing 14 species of fruit and nut species from Azerbaijan and 62 accessions of walnut and almond from Kyrgyzstan. The exploration and exchange will provide genetic diversity previously unavailable to US scientists and other horticultural interests.
2. Germplasm distributions. ARS scientists in Davis, CA, distribute germplasm twice yearly during early Spring and Fall and includes clonal shoots, seed, pollen, and DNA samples. Our customers include private and public sector breeders; geneticists; members of the academic community; and nursery, private, and backyard growers. The demand for fruit and nut crop germplasm has remained steady over the years with minor crops, such as pomegranate and figs in great demand. The Davis repository shipped out 5348 germplasm items during 2009-10. The distribution is essential to increase the genetic diversity in fruit and nut crops facilitating adaptation to changing climate and both insect and disease pressures. This aids in the development of new crop cultivars to address grower and consumer needs.
3. Germplasm characterization. Genetic resources of vine, tree fruit, and nut crop germplasm adapted to Mediterranean climates need to be characterized for researchers and breeders who are developing new crops. ARS scientist in Davis, CA genotyped the entire olive collection of 127 accessions. Three hundred forty accessions representing 52 taxa of Vitis were analyzed to unravel the genetic structure and phylobiogeography. Genetic structure and differentiation were analyzed in cultivated walnut by genotyping the entire collection. The walnut industry/UC Discovery funded project has identified 6000 single nucleotide polymorphisms to be used in genotyping the walnut collection and the data will be merged with twenty-five economic phenotypes collected across two consecutive years to perform further genetic analysis. The collaborative efforts with the plant pathology and genetic group to screen wild walnut germplasm for crown gall, nematode, and Phytophthora is ongoing and the results so far indicate a number of sources of resistance to these soil-borne pathogens. A morphometric analysis on a set of 500 cultivated grape accessions including wine, table and dual-use type using 25 nominal, ordinal, and metric traits has been performed. Characterization of genetic resources increases its usefulness to breeders.Aradhya, M.K., Stover, E.W., Velasco, D., Koehmstedt, A. 2010. Genetic structure and differentiation in cultivated fig (Ficus carica L.). Genetica. 138:681-694