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United States Department of Agriculture

Agricultural Research Service


Location: Nat'l Clonal Germplasm Rep - Tree Fruit & Nut Crops & Grapes

2012 Annual Report

1a. Objectives (from AD-416):
The long-term objective of this project is conservation, characterization, and distribution of plant genetic resources of designated Mediterranean-adapted fruit and nut crops and their wild-species relatives. Over the next 5 years we will focus on the following objectives: Objective 1: Strategically expand the genetic diversity in genebank collections and improve associated information for priority vine, tree fruit, and nut crops (and their wild relatives) adapted to Mediterranean-like climates. Sub-objectives: a. Acquire samples of Vitis, Prunus, Juglans, Pistacia, and Punica from Turkey and the Caucasus nations to fill current gaps in NPGS collections of these priority genera. b. Survey existing U. S. domestic (California and other states) collections of priority crops, identify material that would fill gaps in NPGS collections, and begin acquiring and characterizing them, initially emphasizing Vitis, Prunus, and Ficus cultivated material and germplasm of related wild species. Objective 2: Conserve and regenerate priority vine, tree fruit, and nut crop genetic resources adapted to Mediterranean-like climates efficiently and effectively, and distribute disease-free samples (whenever feasible) and associated information worldwide. Sub-objectives: a. Conserve, regenerate, and distribute vine, tree fruit, and nut genetic resources and associated information, emphasizing Vitis, Prunus, Juglans, Ficus, Olea, and Punica. b. Backup primary collections of Vitis, Prunus, Juglans, Ficus, and Olea, via high-density nurseries, cryopreservation, and tissue culture. c. In collaboration with University of California, Davis Foundation Plant Services and the Canadian Plant Germplasm System, process 70 accessions of NPGS warm-season grapes through quarantine and make them available for distribution. Objective 3: Strategically characterize (“genotype”) and evaluate (“phenotype”) priority vine, tree fruit, and nut crop genetic resources adapted to Mediterranean-like climates for molecular markers and key horticultural traits such as adaptation and product quality. Sub-objectives: a. In cooperation with other ARS and university collaborators, develop and apply new genetic markers for phylogenetic and genetic diversity analyses of priority crops, emphasizing simple sequence repeat (SSR) in Vitis, Prunus, Juglans, Ficus, Olea, and Pistacia. b. Generate SSR “fingerprints” for ca. 1,000 accessions of priority crops, emphasizing Vitis, Prunus, Juglans, Ficus, Olea, and Pistacia, and use them to determine the identity, diversity, and systematic relationships of these genetic resources, and to enhance the effectiveness of genetic resource management. Incorporate characterization data into GRIN and/or other databases. c. Extend ongoing cooperative research to evaluate horticultural quality for ca. 1,000 accessions of Vitis, Prunus, Juglans, Ficus, Olea, and Pistacia, and incorporate phenotypic data into GRIN and/or other databases.

1b. Approach (from AD-416):
Obtain new acquisitions to fill collection gaps and broaden diversity. Make contacts with appropriate institutions to exchange diverse germplasm. Through interactions with CGC's, develop exploration proposals. Engage in cooperative research on cryopreservation of buds. Place evaluation, passport, and source data on GRIN and local database. Expand assessment of genetic diversity by SSR technique and other molecular techniques in Vitis and other genera. Obtain descriptor data for traits of most value to users. Distribute to researchers worldwide.

3. Progress Report:
Based on the multilocus microsatellite genotypes, we identified 25 new genotypes of persimmons from the South Coast Experimental Station (SCES) collection. These genotypes were uniquely different from both NCGR and UCD persimmon collections. These new accessions have been propagated through budding recently on to kaki rootstocks. A set of 190 accessions of apricot from the UCD elite germplasm collection and breeding lines have been genotyped for 12 microsatellite loci and data are currently being analyzed to identify new and unique genotypes to add to NCGR collections. As a part of germplasm management, we have recently analyzed 161 almond seedlings from ~20 progenies with 12 microsatellite loci to identify diverse accessions to propagate and include in the main almond collection block at Wolfskill Experimental Orchard (WEO). The data are currently being analyzed to reveal multilocus genotypes and allele frequencies within and among progenies. This analysis will permit us to identify diverse subset of seedlings to be planted in the main germplasm block. In an industry-funded almond rootstock development program, a second year cycle of interspecific hybrid production involving 25 wild peach (Prunus persica) genotypes as seed parents and eleven wild Prunus spp. as pollen parents was undertaken. Progeny will be evaluated for resistance to soil borne diseases, and also genotyped. Three hundred eighty-four accessions of cultivated walnut (J. regia) have been genotyped using the 6K SNP InfiniumHD iSelect bead chip and data analyzed using GeneomeStudio, and the final genotypes have been assembled for further analyses. Walnut, almond, and grape apical meristems have been placed in vitro with various treatments added to the media. All have established and grown, and grape and almond explants have produced somatic embryos. Walnut produced both axillary and adventitious shoots. This research is aimed at establishing regeneration systems, suitable explants for cryopreservation, and a method to escape viruses and other pathogens. This research is partially funded by industry. Other propagation research has been funded by the California Walnut Board, including walnut shoot forcing, rooting hardwood cuttings, and experiments aimed at improving micropropagation performance. Commercially micropropagated walnut plants are being stored under contrasting refrigeration temperatures for various times up to one year, to determine if they can be produced and stored until planted in a nursery. Cutting propagation research for the purpose of future research is ongoing with mulberries and olives. Figs were propagated this FY for a cultivar trial of new material to the United States in a grower’s orchard in the southern central valley. This work is funded by the California Fig Institute. In an experiment focused on fruit drying quality, 34 persimmon accessions were evaluated at harvest and compared in a drying study. Persimmons shoots were cut and new shoots forced from large stem segments were excised and placed in vitro.

4. Accomplishments
1. Germplasm maintenance. Maintenance of the collections is of upmost importance to keep the plants healthy and thriving. The trees are planted closely, some crops in the collections are aging and require repropagation, and diseases and insects must be controlled. The entire mulberry, olive, and persimmon collections received a second year of thinning out pruning to allow for better size control and light penetration into the trees and all Vitis vinefera canes and rootstocks with foliar phylloxera were removed and destroyed. The fig collection is being repropagated to replace the entire field collection because of age and condition of the trees. The collections were irrigated regularly, received regular weed control, and sprayed when necessary. Pruning provides fruit of better quality, enables phylloxera control, and the collections thrive with re-propagation and with regular maintenance.

2. Germplasm distribution. An important purpose of the Repository is to distribute germplasm to scientists for crop improvement and other investigations. There are many challenges to our food crops and the diversity in the collections can be utilized to improve the plants to meet new threats. Germplasm distribution occurs 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 years with minor crops, such as pomegranate and figs, in great demand. 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.

3. Germplasm conservation and management. Genetic resources of vine, tree fruit and nut germplasm adapted to Mediterranean climates need to be maintained and preserved for food security, with access for researchers and breeders who are developing new crop cultivars. If the genetic resources are not conserved and maintained, they will be lost for current and future generations. The primary collection is maintained in the field at Wolfskill Experimental Orchard, Winters, California, with partial back-ups in containers at the Davis National Clonal Germplasm Repository (NCGR) nursery. New accessions, including those under quarantine, are propagated and maintained at the NCGR Davis nursery until ready for field planting at Wolfskill. It is through use of both a field orchard and container nursery that the collections are conserved and managed at the NCGR-Davis.

4. 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. Lack of characterization renders a genebank of little use to breeders and scientists because they do not know the desirable traits or genotypes of the accessions. A total of 161 almond seedlings from ~20 progenies were compared using 12 microsatellite loci to identify diverse accessions and add them to the collection. One hundred forty accessions with representative samples from 22 wild Juglans spp. and two Pterocarya spp. were genotyped using the 6K (SNP) InfiniumHD iSelect bead chip developed for the cultivated walnut (J. regia). Mulberry and olive accessions were tested for rooting ability, a critical phenotypic trait. The information obtained about the genotypes and phenotypes of these crops in the collections enhances their value to the scientific community.

Review Publications
Wu, J., Gu, Y.Q., Hu, Y., You, F.M., Dandekar, A.M., Leslie, C.A., Aradhya, M.K., Dvorak, J., Luo, M. 2011. Characterizing the walnut genome through analyses of BAC end sequences. Plant Molecular Biology. 78:95-107.

Kong, D. 2011. Somatic embryogenesis in immature cotyledons of Manchurian ash (Fraxinus mandshurica Rupr.). Plant Cell Tissue And Organ Culture. 108:485-492.

Preece, J.E., Smith, J.L. 2012. Phenotypic comparisons between wild relatives and cultivars of kiwifruit, persimmon, mulberry, and olive at the National Clonal Germplasm Repository, Davis, CA. Acta Horticulturae. 948:175-180.

Osman, F., Rwahnih, M., Golino, D., Pitman, T., Cordero, F., Preece, J.E., Rowhani, A. 2012. Evaluation of the phytosanitary status of the prunus species in the national clonal germplasm repository in california; survey of viruses, viroids and phytoplasmas. Journal of Plant Pathology. 94(1):249-253.

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.

Johanning, N.R., Preece, J.E., Young, B.G. 2012. Chilling and chipping influence plant growth and reproduction of star-of-Bethlehem (Ornithogalum umbellatum). Journal of Invasive Plant Science and Management.

Last Modified: 05/27/2017
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