Location: Tropical Crops and Germplasm Research2010 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
The number of germplasm distributions during 2009 was 163 distributions of 196 different accessions with a total of 5,240 propagules in the form of budwood, cuttings, rhizomes, corms, seed and fruit which were made available to researchers and cooperators at the local, national and international level. The second cropping cycle (~2nd year) and evaluation of Musa sp. hybrids for disease resistance to Sigatoka leaf spots has been completed and data is being summarized. In addition to agronomic performance, disease resistance and characterization of phenotypic traits, all accessions in the cacao collection are being categorized as self- compatible or self-incompatible. A collaborative effort between the USDA-ARS Tropical Agriculture Research Station, Mayaguez, the USDA-ARS Subtropical Horticulture Research Station, USDA-ARS Pacific Basin Area Research Center and the USDA-ARS Mid South Area Genomics Laboratory has been initiated to develop and utilize SSR markers to fingerprint tropical fruit genetic resources. The effort focuses on utilizing the fingerprint profiles developed as reference profiles for establishing trueness-to-type for clonally propagated germplasm (cultivars/varieties), estimating genetic diversity and identification of potential gaps in the germplasm collections. Cacao genetic resources in the Dominican Republic are being genetically fingerprinted in a collaborative effort between USDA-ARS Scientists and Land O’Lakes International Development. The cacao genetic resources at the Instituto Dominicano de Investigaciones Agropecuarias y Forestales (IDIAF) were sampled, DNA extracted and fingerprinting has been carried out. In addition, genotyping for an additional ~90 leaf samples were processed form local productive and disease resistant selections made by CONACADO (a large cooperative of small-scale cacao farmers). Local productive selections are being acquired and incorporated into the USDA-ARS-TARS site collection. The project developed a reliable and successful way of grafting Spanish lime for clonal propagation. From this an additional 10 locally propagated accessions have been added to the collection that is being established. Current collection includes ~30 clonally propagated accessions from diverse locations around the island that have been selected for their productivity and for their fruit characteristics.
Irish, B.M., Goenaga Portela, R.J., Zhang, D., Schnell Ii, R.J., Brown, J.S., Motamayor, J. 2010. Microsatellite Fingerprinting of the USDA-ARS Tropical Agriculture Research Station Cacao (Theobroma cacao L.) Germplasm Collection. Crop Science. 50:656-667.