| Summary: | 碩士 === 國立臺灣大學 === 植物病理與微生物學研究所 === 105 === Rice blast disease can seriously damage rice production worldwide, and the use of resistance varieties has been considered the most economically, effective and ecofriendly method for blast control. To provide information needed for introgression of resistance genes, variety deployment and rotation, this study focuses on (1) exploring novel resistance genes/loci by mutation breeding combined with next-generation sequencing technique and (2) identifying the resistance genes/loci in Taiwan high-quality rice varieties through linkage analysis. After 5 generations of NaN3-induced mutation and resistance screening in rice blast nursery, we got 44 NaN3-induced Tainung 82 (TNG82) mutant lines with good resistance. We generated 11 F2 populations from the crosses of “TNG82 x 11 TNG82 mutant lines”, and totally 6300 F2 individuals were evaluated in the upland blast nursery at Chiayi Agricultural Experiment Branch in the second cropping season of 2016. The ratio of resistant to susceptible F2 individuals of “TNG82 x WM1363” is 408: 162, which fits the 3:1 ratio under single-gene inheritance pattern. To identify novel genes associated with resistance, MutMap-plus analysis strategy was applied to compare the SNPs between a pooled sample composed of the most resistant F2 individuals and the parental line TNG82. Four SNPs were identified as the most likely causal mutations: one locates in the gene encoding NBS-LRR protein (Os04g0122000) and three locate in the genes encoding serine/threonine kinase-related receptors (Os04g0103500, Os04g0103700, Os12g0114100). Taikeng 8 (TK8), Taikeng 14 (TK14), and Taitung 30 (TT30) are three widely cultivated Taiwan rice cultivars which have exhibited moderate to high resistance in different rice-growing regions around Taiwan. Previous artificial inoculations and field trials showed that resistance alleles at four loci (Pi2/9, Pik, and Pita/Pita-2) are generally effective against more Taiwanese isolates of rice blast pathogen. F2 populations from the four Taiwan high-quality rice varieties crossed with a susceptible line LTH were developed and evaluated for resistance by artificial inoculation. Linkage analyses based on newly designed polymorphic makers targeting the four R loci revealed that TK14 carries Piz-t, TK8 carries a resistance allele with only one amino acid difference from Pik, and the resistance of TT30 likely come from resistance gene(s) other than Pita at the Pita/Pita-2 locus. The results can serve as useful references for disease control and resistance breeding in the future.
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