Molecular mapping of genes for resistance to rice blast (Pyricularia grisea Sacc)

Two dominant genes conferring complete resistance to specific isolates of the rice blast fungus, Pyricularia grisea Sacc., were located on the molecular map of rice in this study. Pi-l(t) is a blast resistance gene derived from the cultivar 'LAC23'. Its map location was determined using a pair of nearly isogenic lines (NILs) and a B6F3, segregating population from which the isoline was derived. RFLP analysis showed that Pi-l(t) is located near the end of chromosome 11, linked to RZ536 at a distance of 14.0+/-4.5 centiMorgans (cM). A second gene, derived from the cultivar 'Apura', was mapped using a rice doubled-haploid (DH) population. This gene was located on chromosome 12, flanked by RG457 and RG869, at a distance of 13.5+/-4.3 cM and 17.7+/-4.5 cM, respectively. The newly mapped gene on chromosome 12 may be allelic or closely linked to Pi-ta (=Pi-4(t)), a gene derived from 'Tetep' that was previously reported to be linked to RG869 at a distance of 15.4+/-4.7 cM. The usefulness of markers linked to blast resistance genes will be discussed in the context of breeding for durable blast resistance.