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United States Department of Agriculture

Agricultural Research Service


Location: National Clonal Germplasm Repository for Citrus

2011 Annual Report

1a. Objectives (from AD-416)
Maintain high quality of and upgrade citrus variety collection and citrus relative collection.

1b. Approach (from AD-416)
Acquire new potential accessions for the citrus variety collection and citrus relative collection and NCGRCD protected screenhouse collection, evaluate accessions and potential access, update databases appropriately, and maintain collections in good order for efficient utilization.

3. Progress Report
Characterization of accessions in the citrus variety collection for polyembryony: Polyembryony is the ability of some citrus types to produce multiple embryos per seed by a process called nucellar embryony. Nucellar embryos develop asexually within the nucellus tissue of the ovules (precursors to seeds) of each flower. This contrasts to monoembryony which produces single zygotic embryos per seed by sexual hybridization that are a hybrid between both parents. This is important for citrus breeding since varieties that are entirely monoembryonic are preferred as seed parents to ensure that crosses will produce hybrid seed. However polyembryony is a valuable trait for varieties used as seedling rootstocks since the rootstock seedlings should be genetically identical to the seed parent tree. Selected varieties in the citrus variety collection are being tested to determine by germination of sets of 25 or 50 seeds for germination to determine if the seed produces a single (monoembryonic) or multiple (polyembryonic) seedlings. This data will be incorporated into the GRIN and citrus variety collection databases. Facilitated development of web based identification tool to hosts and potential host of U.S. citrus pests and diseases: The Citrus Variety Collection was one of the sites used in the U.S. to study and photograph the citrus hosts of pests and diseases. The pictures and information have been used to develop a comprehensive user-friendly web based identification tool for the USDA APHIS PPQ, cooperators, and the citrus industry when conducting pest and disease surveys. This web site may be seen at The project was monitored by meetings, site visits, e-mail correspondence, and phone calls.

4. Accomplishments

Last Modified: 10/20/2017
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