Location: Subtropical Horticulture Research2008 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.
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
Progress on this project relates to National Program 301, Plant Genetic Resources, Genomics, and Genetics Improvement, Component 2: Crop Informatics, Genomics, and Genetic Analyses. A new database, on which we had been working for a few years, became ready for release to the public and was placed on a new server at the ARS Miami location with the Intellectual Property (IP) address, http://188.8.131.52. The database will have a Universal Resource Locator (URL) as soon as it is assigned by Office of Chief Information Office (OCIO); we have requested http://shrsplantsciences.ars.usda.gov. Cocoa currently has the majority of the data in this database, but the database contains results from avocado and mango, also, and will contain other tropical fruit crops in the future. The database is constantly growing, and has added a pedigree construction algorithm for crops for which data is available. The “CMap” function, a common piece of software in such databases, is currently being added for detailed comparison of pairs or sets of chromosomes of maps contained in the database. In November we moved into a new lab that was not, and is still not, fully functional. We have had serious limitations in our ability to perform molecular genetic analysis because of the non-functionality of many of the lab systems.
1. Analyze Avocado plantings. Description of what was accomplished: Avocado (Persea americana Mill.) fruit were obtained from a commercial orchard in Ventura County, California. The Hass x Bacon mapping population [Mexican x (Guatemalan x Mexican)] has been analyzed with microsatellite makers and outcrossing rates estimated under California conditions have been made. Among the Bacon seedlings 55% (468) resulted from self-pollination while 45% (382) resulted from cross-pollination with Hass. This population has been planted in the field at ARS locations in Miami and Ft. Pierce for further map development and quantitative trait loci (QTL) identification. Description of impact on science and/or technology: This population will be used to produce a genetic linkage map using parents of the Mexican and Guatemalan races. This map will complement our most recent map made using seedlings from parents of West Indian and Guatemalan races. Both will be used for the identification of QTL and for marker assisted selection (MAS). This accomplishment aligns to National Program 301 Plant Genetic Resources, Genomics and Genetic Improvement. Problem Statement 2A: Genome Database Stewardship and Informatics Tool Development.
5. Significant Activities that Support Special Target Populations
Borrone, J.W., Tondo, C.T., Kuhn, D.N., Brown, J.S., Schnell Ii, R.J., Violi, H.A. 2008. Out-crossing in Florida avocados as measured using microsatellite markers. J. Amer. Soc. Hort Sci. 133(2):255-261.