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United States Department of Agriculture

Agricultural Research Service


Location: Tropical Crops and Germplasm Research

2011 Annual Report

1a. Objectives (from AD-416)
Acquire, propagate, and conserve tropical/subtropical crop genetic resources and associated information. Apply new or improved horticultural characterization procedures and genetic marker-based approaches for genetic diversity assessment. Apply new or improved procedures for evaluating tropical/subtropical genetic resources for host-plant resistance to high-priority diseases. Distribute tropical/subtropical crop genetic resources and transfer technologies through GRIN database, internet pages, and scientific publications.

1b. Approach (from AD-416)
Acquisition of new germplasm determined by results from the characterization and evaluation research and from consultations with other crop curators, industry representatives, and members of the Tropical Fruit and Nut Crop Germplasm Committee so as to fill genetic gaps in the collections. Priorities for new germplasm include disease resistant and/or productive accessions. Characterization efforts focus on passport, phenotypic and genotypic descriptors, and evaluation data as well as molecular approaches to determine genetic diversity baselines and horticultural identity. Development of in vitro, medium-term storage techniques for Musa sp. to increase efficiency of propagation and conservation, facilitate distribution and reduce risk of pathogen dissemination. Clonal materials in collections are propagated by grafting or from rhizomes and conserved in field collections. Collections are backed up at other sites to prevent germplasm loss from natural disasters. Field evaluations of potentially disease resistant germplasm are carried out for mango, papaya and Musa sp.

3. Progress Report
This project is a service oriented project with the number of germplasm distributions for the 2010 calendar year, amounting to a total of 115 distributions of 207 different accessions with a total of 4,665 propagules. Tropical germplasm was distributed in the form of budwood, cuttings, rhizomes, corms, seed and fruit, and was made available and distributed to researchers and cooperators at the local, national and international level. A collaborative effort between the several USDA-ARS tropical germplasm repositories and the USDA-ARS, Mississippi to develop and utilize simple sequence repeat (SSR) markers to fingerprint tropical fruit genetic resources continues. The fingerprint profiles developed will be used as reference for establishing trueness-to-type for clonally propagated germplasm, estimating genetic diversity and identification of potential gaps. Datasets and summaries are being generated for Musa spp., Annona spp., Artocarpus spp., lychee, and bamboo. Markers are being validated for rambutan, longan, Spanish lime, star fruit, Garcinia spp., sapodilla, mamey sapote, pineapple, peach palm, papaya, macadamia, Barbados cherry, guava, tamarind and pili nut. A collaborative effort between USDA, scientists at IDIAF (Instituto Dominicano de Investigaciones Agropecuarias) and Land O’Lakes International on DNA fingerprinting of cacao genetic resources in the Dominican Republic has been completed. Data revealed propagation mistakes, estimated genetic diversity and identified unique genotypes within the Dominican cacao genetic resources. Also data was utilized to eliminate propagation mistakes in the clonal cacao germplasm collection and aided in the establishment of a new fully characterized collection. In addition, the USDA-ARS Tropical Agriculture Research Station (TARS) site has incorporated a total of seven highly productive local farmer selections as part of germplasm exchange. A manuscript has been prepared and submitted for publication. First year data is being collected for the Annona spp. germplasm collection. Data collected includes number and weight of fruit, fruit size, and Brix value. Data is shared with the location’s Research Entomologist who is evaluating pheromone treatments within the same germplasm collection. A tissue somatic embryogenesis procedure has been initiated for multiplication and distribution purposes as well as to serve as a backup for cacao accessions held in the primary field site collection. Priority is given to specific accessions unique to the USDA-ARS TARS site and to genetically diverse and agronomically important accessions identified within the collection. Thirty new germplasm accessions of Spanish lime have been established at our field research station in Isabela, Puerto Rico. Each accession is planted in four replicate blocks in a completely randomized block design. A collaborative effort with Bioversity International to develop procedures, based on assessing phenotypic traits, to help clarify Musa spp. taxonomy and to utilize these traits for the correct identification and classification of Musa spp. germplasm is in its first year of full evaluation.

4. Accomplishments

Review Publications
Meerow, A.W., Ayala Silva, T., Irish, B.M. 2010. Turnera diffusa 'Luisa', a drought tolerant small shrub for warm climates. HortScience. 45(12):1895-1896.

Last Modified: 06/24/2017
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