Plant & Animal Genome VI Conference

P31

TOWARD MAP-BASED CLONING OF A GENE FOR PHTOPERIOD SENSITIVE MALE STERILITY IN RICE

National Key Laboratory of Crop Genetic Improvement, Huazhong Agricultural University, Wuhan 430070, China

Photoperiod sensitive male sterility (PSMS) rice, with its fertility regulated by day-length, is a very useful germplasm for hybrid rice development. Using a cross between an indica variety Minghui 63 and 32001S, an indica PSMS line that derived its male sterility gene(s) from the original PSMS mutant Nongken 58S, we previously determined that PSMS was governed by two major loci located on chromosomes 3 and 7, respectively. We also determined that the effect of the locus on chromosome 7 (pms1) was much larger than the one on chromosome 3 (pms2). We are now isolating the (pms1) gene following a map-based cloning approach. Using over 200 highly sterile F₂ individuals from this cross, we resolved the (pms1) locus to a genomic region of less than 4 cM, with the locus residing at 0.51 cM from RG477 (cosegregating with R277 and C67A) on one side and 3.8 cM from R1807 on the other side. Screening of a BAC library using these probes identified three po!sitive clones. RG477, R277 and C67A were located in the same fragment of less than 50 kb long. Interestingly, one of the ends isolated from the positive clone identified by R1807, which is approximately 65 kb in length, cosegregated with RG477, indicating a high likelihood that this clone contains the (pms1) locus. However, this end did not hybridize with the two positive clones containing RG477, suggesting a very uneven distribution of recombination events in this region. We are now sequencing this 65 kb fragment and also isolating cDNAs in this genomic region. The details of the progresses will be presented in the meeting.