Location: Tropical Crops and Germplasm Research2019 Annual Report
1. Efficiently and effectively maintain the safety, genetic integrity, health and viability of priority tropical and subtropical tree fruit, bamboo, and cacao genetic resources and distribute them and associated information worldwide. 1a: Efficiently and effectively safeguard genetic resources. 1b: Back up genetic resource collections. 1c: Distribute pathogen-tested genetic resources. 2. Develop more effective genetic resource maintenance, evaluation, and characterization methods and apply them to priority tropical and subtropical tree fruit, bamboo, and cacao genetic resources. Disseminate evaluation and characterization data via Germplasm Resources Information Network (GRIN)-Global and other data sources. 2a: Characterize and evaluate genetic resources for important horticultural characteristics. 2b: Maintain and enhance access to characterization and evaluation data through GRIN Global, publications, and other databases (MusaNet, ICGD, Bioversity International). 2c: Develop Single nucleotide polymorphisms (SNPs) for cacao and other minor crops within the collections. 3. With other National Plant Germplasm System (NPGS) genebanks and Crop Germplasm Committees, develop, update, document, and implement best management practices and Crop Vulnerability Statements for tropical and subtropical tree fruit, bamboo, and cacao genetic resources and information management.
Plant genetic resources will be efficiently and effectively conserved, backed-up, regenerated, evaluated, and distributed free of diseases. This will be carried out by implementing latest technologies available for field, lab, and greenhouse plant labeling, by maintaining on and off-site backups of critically important germplasm, by field evaluating for important horticultural traits and by indexing/eliminating plant diseases in stock to be distributed. All information associated with plant genetic resources including passport, characterization, and evaluation data will be incorporated into the publicly available Germplasm Resources Information Network (GRIN)-Global database. Development of molecular marker tools is a collaborative effort with other USDA-ARS laboratories and will be used to genotype accessions within the cacao, Annona, sapodilla, Garcinia, sapote and other tropical fruits in the collections, which will aid in the identification of redundancies, discrepancies, and genetic gaps in the collections. In addition, the marker work will complement morphological characterization and stakeholder community input in the development of guidelines to follow for prioritization of future plant introductions. Best management practices and Crop Vulnerability Statements for tropical and subtropical tree fruit, bamboo, and cacao genetic resources and information management will be developed, updated, documented, and implemented.
Progress was made on Sub-objective 1a: Efficiently and effectively safeguard genetic resources. The following research was conducted: 1) As a service oriented project the number of germplasm distributions for FY 2019 amounted to 98. Over 500 different accessions with over 25,000 propagules (i.e., seeds, budwood, Tissue culture) were associated with over 100 collaborators. Tropical germplasm was distributed in the form of scionwood, rhizomes, corms, seed and fruit, and was made available and distributed to researchers and cooperators at locally, 30 states and 3 international organizations; 2) Over 90 tissue culture grown banana (Musa spp.) accessions were received from collaborators. These plants are part of a continued collaborative effort on the verification of genetic integrity of banana genetic resources held in the International Transit Center banana collection in Leuven, Belgium. Many of the plants being field verified have been tissue culture grown for more than ten years and over this time may have accumulated mutations or propagation mistakes. Plants are being acclimatized and will be field established in FY 19-20 for characterization. 3) Over 310 visits/tours to the station grounds for research and education purposes were received during FY 19. Visitors were from 20 states and four foreign countries. Progress was made on Sub-objective 1b: Back up genetic resource collections. The following research was conducted: 1) Over 90% of the Sapodilla field collection has been backed up in greenhouse area; 2) Criollos and Ecuadorian cacao clones were backed up in greenhouse. Progress was made on Sub-objective 1c: Distribute pathogen-tested genetic resources. The following research was conducted: 1) First year of data on fruit resistance/susceptibility to anthracnose, the most important postharvest disease in commercial mango production, has been collected from a segregating maternal half sibling mango population; 2) Ten accessions of banana that include several hybrids from breeding programs with improved disease resistance and productivity were received from Bioversity International. Plants will be available as Tropical Race 4 (TR4) resistant germplasm. This is a devastating disease for banana producers worldwide. TR4 cannot be controlled using fungicides and cannot be eradicated from soil using fumigants; 3) A total of 1,200 flower pollinations have been completed (out of 4,200) in a bi-parental crossing and selfing scheme to try to characterize a set of ten clonal cacao tree selections for their compatibility/incompatibility. The ten cacao selections were released in 2009 and are being recommended for propagation and planting in Puerto Rico. Progress was made on Sub-objective 2a: Characterize and evaluate genetic resources for important horticultural characteristics. The following research was conducted: 1) In collaboration with ARS scientists in Fort Pierce, Florida, certified disease-free budwood pieces of seven mandarin cultivars were received, grafted onto a common rootstock, increased, grafted again onto three rootstocks and established in August 2015 in a replicated trial at two locations for field evaluation for yield, fruit quality traits, and citrus greening incidence. These accessions have never been evaluated in a replicated experiment. Trees in the lower elevation site were severely defoliated and/or had branches broken by Hurricane Maria winds but had recovered; As of FY 19, determination of citrus greening incidence using enzyme-linked immunosorbent assay (ELISA) tests so far are confirming that the disease is widespread at the lower elevation site (100% contamination) but not a problem at the high-elevation (above 600 meters) site; 2) Seven disease-resistant cacao accessions grafted onto EET-400 rootstock were established in a replicated experiment for evaluation of yield, pod index, and organoleptic quality traits. These accessions have never been evaluated in a replicated experiment. Trees are now recovered from defoliation caused by Hurricane Maria and data collection initiated again. A year's worth of data was lost as a result of hurricane damage; 3) Seven breadfruit accessions grafted onto breadnut rootstock were established in a replicated experiment at two locations in August 2015 for evaluation of yield, disease and insect response, canopy volume, and organoleptic quality traits. These accessions have never been evaluated in a replicated experiment. Trees at both locations are fully recovered from damages (defoliation) caused by Hurricane Maria; 4) Eight papaya lines developed by collaborators at the University of the Virgin Islands Experiment Station and ARS scientists were established in a replicated experiment at three locations for field evaluation of yield, fruit quality traits, and papaya ringspot virus (PRSV) tolerance. These accessions have never been evaluated in a replicated experiment. Plantings of Year 2 at the three sites were lost because of hurricane damage and the experiment re-established again in FY19; An experiment to evaluate yield and fruit quality traits of eight jaboticaba selections was established in FY19. These accessions have never been evaluated in a replicated experiment. Progress was made on Sub-objective 2b: Maintain and enhance access to characterization and evaluation data through GRIN Global, publications, and other databases. The following research was conducted: 1) Taxonomic nomenclature as well as links provided on quick response (QR) codes leading to GRIN Global database information were reviewed; 2) Passport information has been updated and descriptors from characterizations as well as voucher images have been loaded into Bioversity databases and GRIN Global for Musa spp. and miscellaneous collections; 3) Final data will be collected before the end of the FY19 for 27 Musa spp. accessions in Field Verification (FV) III as part of a collaborative project with Bioversity International’s Musa International Transit Center. These plants have been in tissue culture for over 10 years in the international collection and need to be field verified and characterized for important phenotypic and agronomic traits. The genetic resources evaluated by this project under this subobjective are critical for diversifying horticultural production systems. Results from these experiments help to fill the knowledge gaps on cropping management systems for tropical/subtropical fruit crops by assisting to identify promising germplasm for use by growers. For example, during FY 19, distributions of the nine high-yielding cacao selections released in 2009 were made to farmers in Puerto Rico. They received 110 budwood pieces, 20 fruit and 80 plants of cacao from these clones. Thanks to this effort a completely new cacao industry is being established in Puerto Rico with clones exclusively developed by ARS scientists in Mayaguez, Puerto Rico. These same clones were requested by collaborating scientists and budwood was sent for grafting and field evaluation in Costa Rica.
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