Plant Genome III Conference Plant Genome III Conference
A powdery mildew (Leveillula taurica (Ldv.) Amaud.) resistance gene (Lv) in tomato has been targeted using RAPD and RFLP markers and found to be located on chromosome 12, between RFLP markers CT211 and CT219, 5.2 cM apart. Using RFLP markers located on chromosome 12, it was shown that approximately one half of chromosome 12, about 42 cM, in the resistant variety is comprised of foreign DNA, presumably introgressed with the resistance gene from the wild species L.chilense. We have screened more than 2000 F2 progenies (>4000 gametes) from a cross between the resistance line (Laurica) and a susceptible line (UC82L) using RFLP markers flanking Lv gene on chromosome 12. More than 80 plants have been identified to be recombinant in this region. These recombinants are being investigated for their disease resistant phenotype. The genetic distance in this region for the F2 population is 2.6 cM as compared to 5.5 cM from L. esculentum X L, pennellii F2 mapping population used in this laboratory. By screening a large segregating population with closely linked molecular markers, the possibility exists to select rare beneficial crossovers and rapidly reduce linkage drag.