Research on wild relatives of fruit and nut crops at the Davis repository

Authors: Aradhya, Mallikarjuna; Preece, John

Submitted to: Acta Horticulturae
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/1/2012
Publication Date: 5/31/2012
Citation: Aradhya, M.K., Preece, J.E. 2012. Research on wild relatives of fruit and nut crops at the Davis repository. Acta Horticulturae. 948:19-32.

Interpretive Summary: The USDA germplasm repository in Davis is responsible for acquiring, conserving and distributing a broad spectrum of diversity of subtropical and temperate fruit and nut species germplasm to stakeholders around the world. Currently the repository holds over 7000 accessions of germplasm including Actinidia (kiwi fruit), Diospyros (persimmon), Ficus (fig), Juglans (walnuts), Morus (mulberry), Olea (olive), Pistacia (pistachio), Prunus (stonefruits and almond), Punica (pomegranate), Vitis (grape), and other minor genera. Wild relatives are widely represented in the collections with nearly 50 % of accessions and >90% of the taxa (196 out a total of 215 taxa) representing the wild gene pools. Research at the repository is mainly focused on genetic characterization of germplasm using molecular markers and morphological traits to quantify and describe genetic structure and differentiation within and among species and gene pools. Various population genetic, multivariate and phylogenetic approaches are utilized to classify and elucidate genetic and evolutionary relationships within and among taxa and gene pools. Most of our crop genera are Tertiary disjuncts with modern distributions showing disjunction between Eurasia and the Americas. There is rich fossil history and excellent opportunities for analyzing the phylogeny and historical biogeography to understand the paleobotanical and evolutionary events that led to the modern disjunctions. In addition to traditional uses of germplasm for genetic improvement of crops, the collections are being increasingly being used in association genetic analyses for gene discovery and to dissect complex economic traits by exploiting historical genetic recombinations that they may have accumulated during their evolutionary history. We will review several studies that we have conducted to illustrate different methods and approaches listed above to characterize germplasm collections, and discuss results and implications for effective conservation, management, and utilization of germplasm collections.

Technical Abstract: The USDA germplasm repository in Davis is responsible for acquiring, conserving and distributing a broad spectrum of diversity of subtropical and temperate fruit and nut species germplasm to stakeholders around the world. Currently the repository holds over 7000 accessions of germplasm including Actinidia (kiwi fruit), Diospyros (persimmon), Ficus (fig), Juglans (walnuts), Morus (mulberry), Olea (olive), Pistacia (pistachio), Prunus (stonefruits and almond), Punica (pomegranate), Vitis (grape), and other minor genera. Wild relatives are widely represented in the collections with nearly 50 % of accessions and >90% of the taxa (196 out a total of 215 taxa) representing the wild gene pools. Research at the repository is mainly focused on genetic characterization of germplasm using molecular markers and morphological traits to quantify and describe genetic structure and differentiation within and among species and gene pools. Various population genetic, multivariate and phylogenetic approaches are utilized to classify and elucidate genetic and evolutionary relationships within and among taxa and gene pools. Most of our crop genera are Tertiary disjuncts with modern distributions showing disjunction between Eurasia and the Americas. There is rich fossil history and excellent opportunities for analyzing the phylogeny and historical biogeography to understand the paleobotanical and evolutionary events that led to the modern disjunctions. In addition to traditional uses of germplasm for genetic improvement of crops, the collections are being increasingly being used in association genetic analyses for gene discovery and to dissect complex economic traits by exploiting historical genetic recombinations that they may have accumulated during their evolutionary history. We will review several studies that we have conducted to illustrate different methods and approaches listed above to characterize germplasm collections, and discuss results and implications for effective conservation, management, and utilization of germplasm collections.