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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

2010 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. Formerly 5320-21000-009-00D (6/08).

3. Progress Report
Lansium domesticum seedlings from 2009 domestic collection in Hilo were planted in the field for observations and selection. Papaya seed regeneration continues at the Paauilo PRSV virus free site where thirteen accessions of selected ‘Kapoho’ solo lines from commercial fields and papaya germplasm accessions were regenerated this year. Transgenic PRSV resistant papaya border plants have been effective over multiple years in keeping susceptible Caricaceae germplasm PRSV-free. A new, late season lychee was identified and propagated to compare to the best current commercial variety for qualities and seasonality. Collected and provided leaf samples of Vasconcellea and Litchi collections to cooperator scientists for molecular markers analysis at USDA/ARS and other institutes. Managed and operated a functional plant germplasm repository of tropical fruit & nut crops in 31 field acres, greenhouses, tissue culture & seed storage on the island of Hawaii consisting of 1078 accessions of 34 genera. On-farm testing of longan pre-harvest disease management impact on post- harvest fruit quality was completed. A leaf bioassay was developed to screen rambutan varieties for Phomopsis resistance. A study on the fruit-fly resistance of ten selected Psidium accessions was initiated and will be on-going through harvest. The ohelo project is continuing with production data and extension outreach to small farmers. Screening techniques for rust and powdery mildew resistance have been developed for ohelo. Introduction and distributions included two introductions, 34 distributions for 355 items; added 549 records to the Germplasm Resource Information Network (GRIN).

4. Accomplishments
1. Maintaining health and viability of germplasm collection. Collections of germplasm must be maintained for optimum health and life. ARS researchers in Hilo, HI managed and operated a functional Plant Germplasm Repository for the national collection of tropical & subtropical fruit and nut crops, provided plant germplasm for scientific research and organized relevant germplasm information for the GRIN national database system. ARS researchers in Hilo, HI collected fifty-two accessions of pineapple during early 2009 responding to the closure of a large pineapple producer in Hawaii. The field collections of litchi are being regenerated; eighteen litchi accessions have been planted on their own roots in a new field. Securing pineapple and litchi germplasm collections will be the future basis of research and breeding efforts.

2. Germplasm collections should contain as much diversity of the species as possible. Lately the exchange and collection of materials has been made more difficult as countries are keeping their natural resources and not distributing them outside of their country. Scientists from Hilo, Miami & Puerto Rico prepared an unfunded Cooperative Research agreement for USDA/ARS, NPGS, Guangxi Subtropical Crops Research Institute (SCRI) & South West Forestry University in China. The agreement has been finalized and forwarded to the cooperating institute. Supporting the strategic expansion and improvement of collections of priority tropical fruit genetic resources and associated information by expanding cooperation with foreign countries allows for additions to the collections which enables future research.

3. Pre-harvest disease management. Disease management is crucial for high quality longan fruit. ARS scientists in Hilo, HI identified pre-harvest longan fungi which adversely effect post-harvest fruit quality and compared varietal differences in response to the fungus. The biofungicide Serenade was used successfully for field control of the disease. Results provide a management strategy for longan fruit disease in the field which will help to enhance post-harvest fruit quality.

Review Publications
Matsumoto Brower, T.K., Zee, F.T., Suzuki, J.Y., Tripathi, S., Carr, J.B., Mackey, B.E. 2010. Determining sex and screening for the adventitious presence of transgenic material in Carica papaya L. seed germplasm. HortScience. 45:161-164.

Last Modified: 06/22/2017
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