Plant & Animal Genomes XIV Conference

January 14-18, 2006
Town & Country Convention Center
San Diego, CA

Citrus Scab Resistance In ‘Fallglo’ Mandarin

David M. O'Malley¹ , Donna Clevenger² , Randall P. Niedz² , Jose X. Chaparro^{1, 2}

¹  Horticultural Sciences Department University of Florida 1301 Fifield Hall PO Box 110690 Gainesville, FL 32611 USA

²  Horticultural Research Laboratory, Agricultural Research Service, U.S. Department of Agriculture 2001 South Rock Road Ft Pierce, FL 34945 USA

Citrus scab disease (Elsinöe fawcetti) is responsible for cosmetic defects on fruit of susceptible citrus cultivars in Florida. The inheritance of citrus scab disease symptoms was studied in a cross of the mandarin cultivar ‘Fallglo’ with an accession of Citrus tachibana. The progeny were exposed to natural inoculum of Elsinöe fawcetti in the field for several years, and disease symptoms on leaves and fruit were assessed in 2, 3, or 4 years. Bulked segregant analysis of symptom-free and heavily infected progeny was carried out using 750 Random Amplified Polymorphic DNA (RAPD) primers. The screening procedure identified 5 RAPD markers in two linkage groups that were associated with disease symptoms. Analysis of the association of disease symptoms with two RAPD markers in 242 progeny revealed strong evidence for two R-genes inherited from ‘Fallgo’. Further study is needed to determine whether the putative R-gene specificities correspond with the two known pathotypes of Elsinöe fawcetti that are endemic in Florida. This marker-disease association will be useful for breeding fresh citrus that is resistant to citrus scab disease.