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J. X. CHAPARRO, Horticulture & Breeding Research Unit, USDA-ARS-U.S. Horticultural Research Laboratory, 2001 S. Rock Rd., Fort Pierce, FL 34945 The availability of biochemical pathway information and the rapid accumulation of sequence information for numerous genes is permitting breeders to look at specific traits from a more mechanistic perspective. The development of rapid and cheap sequencing technology is permitting the rapid scanning of candidate gene sequences to look for sequence variation potentially responsible for phenotypic differences in plants. We are using such an approach to look at the genetic variation for carotenoid pigment accumulation in citrus. Carotenoids, the primary peel and flesh pigments in commercial citrus, demonstrate a wide range of phenotypes for peel and flesh color. Little is known about the genetic control of this commercially important trait. Gene fragments from the carotenoid biosynthetic pathway are being sequenced from a panel of citrus genotypes representing sweet orange (Citrus sinensis), mandarins (C. reticulata), pummelos (C. grandis), and trifoliate orange (Poncirus trifoliata). We have initiated a project to develop nucleic acid sequence based markers for the genes in the biosynthetic pathway. These markers will be used for QTL analysis of peel and flesh color. Progress on the sequencing effort and preliminary analysis of gene copy number and haplotype composition of the different species will be presented.
Session 56, Incorporating emergent technologies into citrus production and processing
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