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United States Department of Agriculture

Agricultural Research Service

Research Project: Pacific Fruit Genetic Resource Management and Sustainable Production Systems

Location: Tropical Plant Genetic Resources and Disease Research

2013 Annual Report

1a. Objectives (from AD-416):
Collect, maintain, evaluate and distribute germplasm of 14 designated tropical fruit and nut crops. (1) Strategically expand and improve collections of priority tropical fruit genetic resources and associated information. (2) Efficiently and effectively conserve and regenerate tropical fruit genetic resources and distribute disease-free samples and associated information woldwide. (3) Characterize and evaluate tropical fruit genetic resources for priority traits, such as biotic and abiotic stress resistance, quality factors, and other horticultural properties.

1b. Approach (from AD-416):
(1) Extend and strengthen research collaboration with plant genetic resource institutes in Southeast Asia to jointly collect and preserve priority landrace population of Litchi and Nephelium. Identify and establish contacts in Central America to collect Carica and Vasconcellea germplasm. Survey existing U.S. domestic collections of tropical fruit genetic resources to identify material that would fill gaps in NPGS collection, acquiring and characterizing them. (2) Maintenance and research on 14 designated crops in field plantings, tissue culture and seed storage and regeneration. Optimize regeneration and long-term low temperature storage procedures for Carica, Vasconcellea, Macadamia and Canarium seeds. Develop and implement the means for effectively managing PRSV disease in gene bank plantings of Carica and Vasconcellea. Utilize transgenic PRSV resistant papaya as border plantings to facilitate the regeneration of tradional non-transgenic papaya germplasm in PRSV infected area. Detect, characterize and document fungal pathogens which could impede the distribution of disease free rambutan and longan germplasm. (3) Morphologically characterize, evaluate, and document the horticultural qualities of priority tropical fruit crops. Incorporate evaluation and characterization data into the ARS Germplasm Resources Information Network (GRIN). Develop rapid and accuate diagnostic assays for evaluating the susceptibility of rambutan and longan to fungal diseases. Determine the effect of environment and crop management on timing and uniformity of flowering for litchi, longan, and rambutan to improve descriptor data collection and to enhance their commercial appeal as crops.

3. Progress Report:
This is the final report for this project, terminated in March of 2013, and replaced with project 5320-21000-014-00D, "Pacific Tropical/Subtropical Fruit and Nut Genetic Resource Management and Sustainable Production Systems". We introduced and maintained a backup collection of 29 cacao accessions from Miami and Puerto Rico. We continued quarantine transfer of USDA avocado germplasm from Miami to Hilo through Fort Detrick, Maryland; 23 avocado accessions tested free of Avocado Sunblotch viroid and no laurel wilt sign was observed after being quarantined in Hilo, and secured in a designated screenhouse. A late season lychee and pineapple germplasm were added to the collection. Orchard plantings older than 25 years were propagated on their own roots and replanted in different fields to ensure long term germplasm integrity and vigor. These crops included guava (Psidium), carambola (Averrhoa) and breadfruit (Artocarpus). Leaf samples of Vasconcellea, Litchi and Macadamia were collected and provided to the National Plant Germplasm System (NPGS) and scientists for characterization studies. The grant-supported ohelo (Vaccinium reticulatum) project was completed and 3 ohelo selections were released. A germplasm exchange relationship with 3 Crop Research Institutes (2 in China and 1 in Japan) was established; 39 papaya and Vasconcellea accessions were regenerated, and 2 plantings of 13 selected ‘Kapoho’ papaya lines were completed. The virus protection effect of transgenic PRSV resistant papaya plants as a trap border to a planting of traditional papayas, and the pollen drift potential of transgenic papaya were determined. Papaya seeds from 3 cultivars were stored at 4°C, -80°C and -196°C, and are under evaluation for viability by germination. On-farm testing of pre-harvest disease management impacts on post-harvest fruit quality of longan was completed. The host resistance of 10 guava accessions to Pestalotiopsis and fruit flies were analyzed. New techniques for screening resistant guava varieties were provided to a number of foreign countries, including Mexico, Costa Rica, Columbia and Chile. Techniques developed for identification and host/pathogen interaction studies are currently being used at Mexico’s Agricultural, Livestock and Forestry Research Organization (INIFAP). Chemical management procedures for Macadamia Quick Decline disease and the disease etiology for Phomopsis and leaf bioassay for rambutan disease screening were established. The genes involved in flowering of longan and lychee were isolated and evaluated and the final report was submitted. Fruit traits, yield, labor and post-harvest quality of longan were completed for foliar fertilizer-based fruit thinning. We introduced 120 accessions, made 222 distributions for 1308 items, and added 14,695 Germplasm Resource Information System (GRIN) records. Tropical fruit and nut germplasm was evaluated and 58 ‘Pathogen Testing’ entries were compiled for entry into GRIN. This research provides critical information for the management, preservation and distribution of valuable plant genetic resources for future conservation and crop improvement strategies.

4. Accomplishments

Review Publications
Ayala Silva, T., Schnell II, R.J., Goenaga, R.J., Zee, F.T., Irish, B.M. 2013. The National Plant Germplasm System: the subtropical and tropical fruit genebanks. Acta Horticulturae. 975:43-54.

Gschwend, A.R., Wai, C., Zee, F.T., Arumuganathan, A.K., Ming, R. 2012. Genome size variation among sex types in dioecious and triecious Caricaceae species. Euphytica International Journal on Plant Breeding. DOI: 10.1007/s10681-012-0815-9.

Last Modified: 10/18/2017
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