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 are growing well at the field in Waiakea, Hawaii and expect to produce in 2017. Paauilo PRSV virus-free field remained virus-free, and will continue to be used for papaya seed regeneration. Cover crops are tested in Paauilo to assure soil management and provide for crop rotation. Transgenic PRSV resistant papaya border plants have been effective at Waiakea over multiple years in keeping susceptible Carica germplasm PRSV-free. A small planting of non-transgenic papaya accessions were planted two years after the planting of the transgenic papaya to determine if the area remains virus free. Eighteen accessions of avocado received from Fort Detrick in 2010. Fifteen of the 18 accessions were successfully grafted and maintained at the Hilo greenhouse. Eleven more accessions have been received and grafted. A late season lychee selection was planted with “Kaimana” to compare growth and fruit qualities, the first step in a variety evaluation. The final report has been filed for “Improving flowering of longan and lychee in Hawaii”. We have isolated genes involved in flowering in both longan and lychee and are currently evaluating their role in regulating flowering in these two crops. Work has been completed on the comparison of fruit traits, yield, labor and post-harvest quality using foliar fertilizer spray as an alternative to hand thinning longan fruit on potassium chlorate treated trees with larger fruit loads. Provided plant tissue and seeds of Vasconcellea spp. to scientists nationally for molecular analysis and taxonomic studies; this service resulted in increased new sources of Vasconcellea for our germplasm exchange program. The unit managed and operated a functional plant germplasm repository of tropical fruit and nut crops in 31 field acres, greenhouses, tissue culture and seed storage on the island of Hawaii consisting of 1448 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 preliminary comparison of fruit-fly tolerance between ten Psidium accessions completed. The ohelo project is concluding as scheduled. Preliminary information on plant adaptation, nursery, disease and production management practices are compiled and published as extension information. Berry production reached the set goal during May and July 2011 with 50 lbs of fruit harvested in the three month period. Over 95 lbs of frozen ohelo were provided to chefs and value added research cooperators for product testing. Three ohelo selections were released by USDA/ARS, these varieties are maintained in the public domain at the Corvallis repository. These varieties are also available for commercial uses and can be ordered from a commercial tissue culture laboratory. Screening techniques for rust and powdery mildew resistance have been developed for ohelo. Introduction and distributions included 39 introductions, 62 distributions for 324 items; added 2481 records to the Germplasm Resource Information Network (GRIN).
1. Maintaining health and viability of germplasm collection. Maintenance of germplasm requires rejuventation of crops to ensure healthy germplasm material for distribution and characterization. The curator and ARS scientists in Hilo, Hawaii initiated re-propagation of older trees to rejuvenate the collection and to manage tree size. The new plantings, Guava – Psidium guajava, Carambola – Averrhoa carambola, Lychee – Litchi chinensis, and Bread fruit – Artocarpus altilis, are accessions on their own roots (not grafted) to eliminate the potential for rootstock overgrowth. This will ensure the integrity and viability of the germplasm collection and distribution.
Follett, P.A., Zee, F.T., Hamasaki, R.T., Hummer, K.E., Nakamoto, S.T. 2011. Susceptibility of low-chill blueberry cultivars to oriental fruit fly, mediterranean fruit fly, and melon fly (Diptera: Tephritidae). Journal of Economic Entomology. 104:566-570.