| Rice blast is the most widely distributed and the most severe rice disease worldwide. In order to keep the sustainable production of rice, solving the problem of rice blast has always been one priority research project worldwide. The continuous epidemics of rice blast became in recent years are due to the high variability in the pathogenicity of M. grisea isolates and lacking of varieties with durable and broad-spectrum resistance. Therefore, the discovery and utilization of disease-resistant genes and development of broad-spectrum resistant varieties by pyramiding multiple resistant genes have been considered to be the most effective way to control rice blast.The india cultivar (cv.) 93-11 is well known for high yield, good quality and resistance to multiple diseases. In the present study, the evaluation of cv. 9311 for their resistance against 352 indica- and japonica-blast isolates collected from different japonica and indica rice cultivated regions shows that this cultivar can resist 72.2% of all tested isolates, and particularly 81.2% of the 154 japonica-derived isolates, indicating that cv. 93-11 could be used as a broad-spectrum blast-resistant resource in japonica rice breeding program.. The genetic analysis of cv 9311 by inoculating F2 and F3 populations derived from a cross of LTH×9311 with two rice blast isolates, 001-99-1 and 99-26-2, showed that the resistance of this cultivar was conferred by two independent genes, in which one gene, tentatively designed as Pi93-1(t), was effective to the isolate 001-99-1, and the other gene, tentatively designed as Pi93-2(t), effective to isolate 99-26-2.To finely map the gene Pi93-1(t), we developed a mapping population consisting of 1698 F2 plants susceptible to isolate 001-99-1, and finally mapped the gene Pi93-1(t) within a 0.22 cM interval flanked by two marker 11-B14 (0.17cM) and Indel11-E13 (0.05 cM) on chromosome 11, where three markers, 11-H6, 11-H4 and 11-H2, co-segregated with it, by using BSA-RCA strategy and molecular markers. Using the same method, we screened out 539 F2 plants extremely susceptible to isolate 99-26-2 and mapped the gene Pi93-2(t) within a 0.55 cM interval flanked by two Indel markers Indel12-6 and 12-G8 on chromosome 12, where 2 markers,Indel12-5 and RM27990,co-segregated with it.Inoculation test of rice cultivars and monogenetic lines each harbouring the target genes using differential isolates showed that Pi93-1(t) is a novel blast resistance gene, and Pi93-2(t) is embedded in the same gene cluster in 9311 with Pi41(t) but different from the mapped genes, Pita, Pita-2, Pi12(t), Pi19(t), Pi20(t), Pi39(t) and Pi41(t).Based on the annotated sequence of 9311 in the Gramene and Orygenesdb database, we determined three NBS-LRR genes are candidates for Pi93-1(t), and one NBS-LRR gene is candidate for Pi93-2(t).
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