GENETIC MAPPING OF RANDOM AMPLIFIED POLYMORPHIC DNA (RAPD) MARKERS IN CITRUS

Genetic mapping with RAPD markers has been initiated in Citrus . Reproducible polymorphism of amplified DNA fragments has been revealed with approximately half of the 80 random primers thus far tested. Apparent segregating loci revealed with these primers are being analyzed for reproducibility, inheritance, and linkage using 60 BC, progeny from an intergeneric cross of Citrus grandis (L.) Osb. × [ C. grandis × Poncirus trifoliata (L.) Raf.]. This progeny population has been previously used to map 57 isozyme and RFLP markers [Durham et al., Theor. Appl. Genet. (1992) 84:39]. Thus far 70 RAPD markers have been placed on the map; a current map will be presented. We hope to use a highly populated linkage map to map quantitative trait loci for cold tolerance in this cross between very cold-sensitive C. grandis and extremely cold-hardy P. trifoliata. As a part of this project, we have thus far isolated 6 unique cold acclimation responsive cDNA clones through differential screening of a library constructed from cold acclimated tissue of P. trifoliata . Work is also in progress to place these clones on the linkage map.