RFLP MAPPING OF ISOZYMES, RAPD AND QTLS FOR GRAIN SHAPE, BROWN PLANTHOPPER RESISTANCE IN A DOUBLED HAPLOID RICE POPULATION

We have developed an RFLP framework map with 146 RFLP markers based on a doubled haploid population derived from a cross between an indica v ariety IR64 and a japonica variety Azucena. The population carries 50. 2% of IR64 loci and 49.8% of Azucena loci, indicating an equal amount of genetic materials from each parent has been transmitted to the prog enies through anther culture. However, some markers show segregation d istortion. These distorted marker loci are located on 10 chromosomal s egments. Using this map we were able to place 8 isozymes, 14 RAPDs, 12 cloned genes, I gene for brown planthopper (BPH) resistance, and 12 Q TLs for grain length, grain width and length/width ratio onto rice chr omosomes. The major gene for BPH resistance was mapped on chromosome 1 2 near RG463 and isozyme Sdh-1. Most of the QTLs identified for the th ree grain characters were closely linked on chromosomes 1, 2, 3 and 10 . We concluded that the RFLP framework map presented here will be usef ul for mapping other genes segregating in this doubled haploid populat ion. Thus rapid generation of doubled haploid lines and their unbiased segregation make it very attractive for gene mapping.