RFLP mapping of isozymes, RAPD and QTLs for grain shape, brown planthopper resistance in a doubled haploid rice population.
An RFLP framework map with 146 RFLP markers was developed using a doubled haploid population derived from a cross between the indica variety IR64 and the japonica variety Azucena. The population carries 50.2% of IR64 loci and 49.8% of Azucena loci, indicating that an equal amount of genetic materials from each parent has been transmitted to the progenies through anther culture. However, some markers showed segregation distortion. These distorted marker loci were located on 10 chromosomal segments. Using this map, 8 isoenzymes, 14 RAPDs, 12 cloned genes, 1 gene for brown planthopper (BPH) [Nilaparvata lugens] resistance, and 12 QTLs for grain length, grain width and length/width ratio were located on the rice chromosomes. The major gene for BPH resistance was mapped on chromosome 12 near RG463 and isoenzyme gene Sdh-1 (shikimate dehydrogenase). Most of the QTLs identified for the three grain characters were closely linked on chromosomes 1, 2, 3 and 10. It is concluded that the RFLP framework map presented here will be useful for mapping other genes segregating in this doubled haploid population. Thus, rapid generation of doubled haploid lines and their unbiased segregation make them very attractive for gene mapping.