LINKAGE MAPPING OF ESTS DERIVED FROM Citrus FRUIT cDNA

National Institute of Fruit Tree Science, Department of Citriculture, Okitsu, Shimizu, Shizuoka 424-0292, JAPAN

CAPS markers were developed to construct a linkage map of Citrus. STS primers were designed on the sequence of genes and ESTs of cDNA libraries from Citrus fruit and seed at different developmental stages. A total of 344 ESTs and genes were tested and 214 (62 %) successfully generated STS fragment. The fragment was digested by 16 restriction enzymes to detect CAPS, and 114 STSs (33 % of total ESTs) revealed polymorphisms among 3 Citrus cultivars. These CAPS markers were applied to the segregation analysis in BC₁ progenies between Citrus unshiu (satsuma mandarin cv. Miyagawa wase) and C. sinensis (sweet orange cv. Trovita orange). A linkage map was constructed by 73 CAPS markers, 3 RAPD markers, 3 isozymes and 3 characteristic markers, and among them 76 markers were joined into 10 linkage groups covering a total of 499 cM with average map distance of 6.7 cM. In a preliminary test to localize fruit characteristics, polyembryony was linked with ss2 locus (sucrose synthase-2) but other 2 characteristics were not linked to any CAPS markers.