| 論文英文摘要 |
Rice is an important staple crop. Rice blast caused by Pyricularia oryzae can seriously affect rice production, and the use of genetic resistance is the most effective and eco-friendly method to control this disease. Tainung 82 (TNG82) is a japonica rice susceptible to rice blast. Forty-four rice blast resistance lines were generated after five generations of sodium azide mutagenesis and disease screening in the blast nursery. In this study, WM1370, the mutant line resistant to rice blast and sheath blight, was inoculated with nine local P. oryzae isolates. WM1370 showed broad-spectrum resistance to all nine isolates. Additionally, TNG82 and WM1370 were sequenced for known rice blast resistance loci Pi2/9, Pik, Pita, and Ptr. TNG82 carries Pik-s and susceptibility alleles at Pi2/9, Pita, and Ptr. WM1370 carries resistance alleles at Pik-s and Pita, and have different mutations at Pi2/9 and Ptr. To understand the genetics of resistance in WM1370, 636 F_2 progenies of WM1370 crossed with the susceptible indica cultivar CO39 were evaluated for disease severity in Chiayi upland blast nursery in 2018. Bulked segregant analysis using 84 simple sequence repeat (SSR) markers suggested that the resistance was associated with two markers located at 3 Mb and 17.8 Mb on chromosome 12. Linkage analysis was conducted using CO39 x WM1370 F_(2:3) to F_(2:5) progenies, by evaluating their resistance in Chiayi upland blast nursery in 2019-2021 and their genotypes at five SSR, eight KBioscience competitive allele-specific PCR (KASP), and ten insertion-deletion (Indel) markers. The resistance segment of WM1370 was fine-mapped to approximately 10.7 to 14.6 Mb, which contains Ptr [with predicted one amino acid difference (L763F) from the allelic protein in the resistance cultivar, Katy]. The resistance segment across Pita (10.6 Mb) and the resistance locus at 10.7-14.6 Mb on chromosome 12 in WM1370, and the newly developed markers tightly linked to the resistance segment, can serve as an important basis for the application of WM1370. It is expected to expand the pool of rice blast resistance genes in Taiwan, and promote the breeding of new resistant varieties in the future. |