Location: Subtropical Horticulture Research2009 Annual Report
1a. Objectives (from AD-416)
The primary goals for this project are to conserve, collect, evaluate, and distribute germplasm and associated information for subtropical/tropical fruit, sugarcane, and Tripsacum. A secondary goal is to investigate the genetic basis of important horticultural traits such as disease resistance and to select improved germplasm. Molecular markers have been developed for genetic diversity analysis and for the production of molecular genetic linkage maps. Families of avocado, mango, and jackfruit have been produced that should allow the mapping of Quantitative Trait Loci (QTL) involved with disease resistance, fruit quality, and yield. A candidate gene approach (CGA) is also being used to find genes involved with disease resistance and for control of flowering. Establish at other National Plant Germplasm System sites duplicate, back-up field plantings of Subtropical Horticulture Research Station priority germplasm; rejuvenate current Subtropical Horticulture Research Station field collections in Miami; and, as determined by annual demand, expand the curatorial capacity for distributing germplasm of sugarcane and tropical/subtropical tree crops.
1b. Approach (from AD-416)
Maintain healthy field collections of current accessions of tropical/subtropical fruit trees and grasses. We recognize that the genetic diversity available in tropical fruit species is not fully represented in the current collections. Significant loss of biodiversity and increasing difficulty in collecting germplasm in tropical countries makes it imperative that new accessions be collected as quickly as possible. Implement improved horticultural practices to ensure the longevity of current collections by re-propagating old clones on new rootstocks in new fields. Add new accessions as they become available from foreign collaborators and breeding programs. Because Most of the species and location priorities for collection have been established, it is essential that we support international collecting expeditions with appropriate benefit sharing. After quarantine requirements have been satisfied, the new accessions will be maintained in field plantings. Backup core collections have been established in Mayaguez, Puerto Rico or Hilo, Hawaii. Adequate daily maintenance and periodic replanting of the sugarcane and Tripsacum collection is required to maintain these genetic resources, some 1,800 accessions, as healthy clones.
3. Progress Report
A genetic linkage map has been developed from a population resulting from a Simmonds x Tonnage cross. This is the first highly resolved linkage map for avocado and will facilitate QTL location for important traits. The redbay ambrosia beetle, Xyloborus glabratus Eichhoff was introduced into the U.S. near Savannah, GA in 2002. Within three years, a wilt and dying of the red bay tree, Persea borbonia was associated with the insect and its associated symbiotic fungus, Raffaelea lauricola. Laurel wilt disease has caused very high mortality of redbay trees along the Atlantic coast from south of Charleston, SC, to Okeechobee County, FL. The fungus infects and kills other members of Lauraceae including avocado, Persea americana Mill. USDA, ARS, NPGS collection of avocado is conserved at the NGR in Miami-Dade County Florida. Although the avocado collection is currently free from the ambrosia beetle and the laurel wilt disease, it is believed to be only a matter of time before this insect/disease complex reaches the collection. We have developed a protocol to secure the USDA, ARS, NPGS avocado collection at Miami by establishing a backup collection in Hawaii and in California.
1. Analyze avocado plantings. A genetic linkage map has been developed from a population resulting from a Simmonds x Tonnage cross. This is the first highly resolved linkage map for avocado and will facilitate Quantitative Trait Loci (QTL) location for important traits.
2. Short Title: Threat of Laurel Wilt. Laurel wilt disease has caused very high mortality of redbay trees along the Atlantic coast from south of Charleston, SC, to Okeechobee County, FL. The fungus infects and kills other members of Lauraceae including avocado, Persea americana Mill. The USDA, ARS, NPGS collection of avocado is conserved at the NGR in Miami-Dade County Florida. A protocol was developed to secure the avocado collection from the threat of Laurel Wilt. The protocol has three different activities. First, using the ARS Foreign Disease/Weed Science lab in Ft. Detrick, MD as an intermediate quarantine, rootstocks have been grown from seed sent from Miami. Staff from the NGR in Miami will hand carry scions to Ft. Detrick and graft them onto the rootstocks this fall. The grafted scions will remain in the greenhouse for one year or until accessions are successfully established in Hawaii and California. Second, a method for chemical control of the pathogen has been developed and deployed at the NGR-Miami and third we are backing up all avocado germplasm in an insect proof greenhouse at the NGR-Miami.
Ayala Silva, T., Schnell Ii, R.J., Meerow, A.W., Brown, J.S., Gordon, G.G. 2009. A Study on the Morphological and PhysicoChemical Characteristics of Five Cooking Bananas. Journal of Agronomy. P.1-6.
Iyer, C.P., Schnell II, R.J. 2009. Classical Breeding and Genetics: In the Mango, Botany, production and uses Vol II.. The Mango. Ed. Richard E. Litz. CAB International ISBN 978 1 84593 489 7 pages 67-96.
Irish, B.M., Crespo, A., Goenaga, R.J., Ayala Silva, T., Niedz, R.P. 2009. Ploidy level and genomic composition of the USDA-ARS Tropical Agriculture Research Station Musa sp. Germplasm Collection. Journal of Agriculture of the University of Puerto Rico, 93(1-2):1-22.
Borrone, J., Brown, J.S., Tondo, C.L., Mauro-Herrera, M., Kuhn, D.N., Violi, H., Sautter, R.T., Schnell Ii, R.J. 2009. An EST-SSR based linkage map for Persea americana Mill. (avocado). Tree Genetics and Genomes. 10.1007/s11295-009-0208-y
Ying, Z., Davenport, T.L., Faber, B., Zhang, T., Schnell Ii, R.J., Tondo, C.L. 2009. Re-evaluation of honeybees and wind on pollination of avocado. Journal of Horticultural Science and Biotechnology. 84(3)255-260.