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United States Department of Agriculture

Agricultural Research Service


Location: Tropical Crops and Germplasm Research

2012 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 2011 calendar year, amounting to a total of 196 distributions of 204 different accessions with a total of 33,304 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 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 germplasm continues with a second cropping cycle and is scheduled to conclude this year. A second year of data is being collected in 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. Two separate research projects genotyping cacao are underway. Leaf samples are being collected, DNA is being extracted, and samples are being sent to collaborators for genotyping. The first project involves DNA samples for each accession in the germplasm collection. The second project involves the sampling of local/naturalized cacao populations on the island of Puerto Rico. Both projects will be genotyped with a standard set of close to 100 single nucleotide polymorphism (SNP) markers and reference profiles will be incorporated into the GRIN database. The Musa spp. field germplasm collection has been re-established at the USDA-ARS TARS research farm in Isabela. A single plant from the tissue culture collection was planted next to as single traditionally propagated field corm. This was done in order to compare phenotypic differences among clonal plants and to verify tissue culture plants were true-to-type. In addition, field accessions were arranged based on their genomic composition in order to identify clonal accession with different accession names in order to rationalize the collection. Successful in vitro micropropagation was achieved for two of the large clumping tropical bamboo accessions held at the site. The in vitro cultures will serve as laboratory back up plants and will enable our site to more readily distribute these genetic resources. Efforts continue to optimize the technique for additional topical bamboo accessions. Cacao germplasm accessions continue to be backed up in the laboratory using somatic embryogenesis (a tissue culture propagation technique). In addition, cacao germplasm accessions are being characterized for the compatibility/incompatibility trait in flowers, a trait critical in fruit set and production.

4. Accomplishments

Review Publications
Verle Rodriguez, J.C., Irish, B.M. 2011. Effect of coconut palm proximities and Musa spp. germplasm resistance to colonization by Raoiella indica (Acari: Tenuipalpidae). Experimental and Applied Acarology. DOI:10.1007/S10493-011-9484-Y.

Last Modified: 05/26/2017
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