| Rice blast, caused by Magnaporthe oryzae.is one of the most serious and wides pread diseases of rice worldwide. The exploitation 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.Minghui 63 was one of the most famous three-line hybrid rice restorers, and s howed sustainable broad-spectrum resistance to rice blast in China. In this study, we conducted the genetic analysis and mapping of resistance genes in Minghui 63 for its blast resistance by inoculating F2 and F3 populations derived from a cross LTH x Minghui 63 with two differential isolates HD12, GDBR8, which collected from H eilongjiang Province and Guangdong province, respectively. The result showed that t he resistance of this cultivar was conferred by one single gene, tentatively designed as Pimh(t).To finely map the gene Pimh(t), we developed a mapping population consisting of 563 F2 plants susceptible to isolate HD12, and finally mapped the gene Pimh(t) within a 0.50cM interval on the chromosome 2 by using BSA-RCA strategy and molecular markers, which was flanked by two marker AP28SR2(0.35cM) and RM 3542(0.17cM) on chromosome 2, and co-segregated with Indel marker InB. Accordi ng to Nipponbare sequence, the gene Pimh(t) was further anchored within 58kb inte rval, flankedcovered by by two BAC clones AP04028 and AP04048.In order to determine the identity of the gene Pimh(t) with the known resistan ce genes, Pi-d(t), Pi-14(t), Pi-16(t), Pib and Pi25(t), in its vicinity on the chromoso me 2, several experimental assays, such as linkage analysis between Pimh(t) and the above genes, resistance evaluation of Minghui 63 and these genes'donors against differential isolates, and specific amplification of Pib locus using functional markers, etc. The results showed that the gene Pimh(t) should be different from all of the a bove known genes, but could be allelic to Pib. Based on the DNA sequence of Nip ponbare, ten candidate genes was predicted within the 58 kb targeting for the gene Pimh(t) by using gene prediction programs including Orygenesdb and Gramene, amo ng which two genes, LOC_Os02g57310 and LOC_Os02g57305, belong to the NBS-LRR type of plant resistance genes, and were preferred as candidate genes for Pimh (t) cloning.In order to determine if some other blast resistance genes or QTLs in Minghui 63, one RIL population of Zhenshan 97×Minghui 63 were repeatedly inoculated with three differential isolates ZB15,50-3 and 2000-21, and analyzed using selective genotyping method of QTL IciMapping. As the result, three major QTLs were dete cted from Minghui 63. Among them, one major QTL, which was the same position as the resistance genes Pimh(t), i.e., the interval between markers RM213 and RM 208 on chromosome 2, conferred resistance against all these differential isolate ZB1 5,50-3 and 2000-21, and was deduced to be the gene Pimh(t) in essence. The oth er two major QTLs were located between molecular markers R1164 and RZ698 on chromosome 9 and between molecular markers R1629 and C483 on chromosome 8, respectively, and the former one conferred resistance against both of the isolates Z B15 and 50-3, and the latter one conferred resistance to the isolate 2000-21 only. A t present, we are trying to finely map the above three major QTLs through construc ting secondary populations. |
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