ALLELISM OF BLAST RESISTANCE GENES IN NEAR-ISOGENIC LINES OF RICE

A set of near-isogenic lines (NILs) for rice blast resistance was previously developed in the genetic background of indica rice cultivar CO39. The 22 CO39 NILs carry five blast resistance genes. In this report, allelism between these resistance genes in the CO39 NILs and Kiyosawa's Differential series of cultivars was analyzed. Pi-1(t), carried by the NILs in group I, was closely linked to Pi-k on chromosome 11, with a recombination value of 6.1 +/- 1.7% (standard error [SE]). Pi-2(t), carried by the NILs in group II, was allelic or closely linked to Pi-z on chromosome 6. Pi-3(t), present in the group V NIL, was closely linked to Pi-i, with a recombination value of 7.0 +/- 2.6% SE, Pi-4(a)(t), carried by the NILs in groups III and IV, was allelic or closely linked and possibly identical to Pi-ta on chromosome 12. The NIL in group VI carried Pi-4(a)(t) and a gene with an unknown identity, which was not Pi-4(b)(t). At present, a set of NILs consisting of C10ILAC (Pi-1(t)), C101A51 (Pi-2(t)), C104PKT (Pi-3(t)), C101PKT(Pi-4(a)(t)), and C105TTP-4L23 (Pi-4(a)(t)+Pi-?) is available for use as differentials.