Inheritance Analysis And Mapping Of Resistance Genes To Rice Blast In Two Japonica Rice Landraces, And Study On Relationship Between DNA Fingertypes And Pathotypes Of Blast Fungus

As the major human staple crop, rice is expected to be crucial to the sustenance of the growing global population well in this century. Rice blast disease, which is caused by the fungal agent, Magnaporthe grisea, represents one of the greatest pathological threats to rice crops. To overcome this disease, utility of durable resistance culitars is considered as the most economical and effective method.In this perper, three differential systems including seven Chinese differentials, seven near-isogenic lines from Lijiangxintuanheigu backcross and twelve Japanese differential cultivars with a single R gene, were evaluated by 31 blast isolates. The Japanese differential system is endowed with great ability to identify isolates, by which 23 pathotypes were identified from all isolates. 15 pathotypes were differentiated by near-isogenic lines and 11 of all isolates are classified to pathotype LI by reason that the differential system was consist of few cultivars each with single R gene which was charactered with comprehensive resistance to rice blast isolates. Only 11 pathotypes were identified by Chinese differentials and more than half of 31 isolates belong to race ZG1 because of each Chinese differential in possession of many R genes to rice blast except Lijiangxintuanheigu. Different resistance spectrums were shown in some cultivars with the same R gene. The cultivars with single R gene, Pi-km, Pi-ta, Pi-zt, Pi-k, Pi-ta2 or Pi-z,was endowed with comprehensive ability to resistance to blast isolates. Japonica cultivars Heikezijing (HKZJ), Tieganqing(TGQ), Bobao, R917 and Shennong 1033 from China showed highly resistant to most of the tested isolates of rice blast fungus Magnaporthe grisea, from which it was presumed that these cultivars possess of many R genes to blast respectively.The F1, F2 and RILs populations from the cross between the resistant varieties Heikezijing, Tieganqing and the susceptible variety Lijiangxintuanheigu (LJXTHG) were inoculated by spray with three Japanese strains Ken 54-04, Hoku 1 and P-2b, and four Chinese isolates in seedling stages. Based on the R:S ratios of segregation in F2 and RIL populations, there were two independent dominant genes in Heikezijing in responsible for resistance to strain Ken 54-04, and one dominant R gene to strain Hoku 1, P-2b, JS01(ZGl), ZJOl(ZGl), 184(ZC5) and NH02-4101 respectively. So total eight different R genes in Heikezijing were tested with the seven isolates (strains). The allelic test indicated that the gene in Heikezijing resistance to Hoku 1 is non-allelic to loci of Pi-k, Pi-z, Pi-ta, Pi-b and Pi-t, also neither Pi-i nor Pi-a gene. It is concluded that R gene to Hoku 1 in Heikezijing is not presence in 12 Japanese differential cultivars. Inanother cultivar Tieganqing, there were two independent dominant genes resistance to strain Ken 54-04 and the other one to strain Hoku 1. These three R gene was tested non-allelic.The parents, Fi, F2, F3 from the cross Heikezijing/Suyunuo and Tieganqing/Suyunuo were inoculated with rice blast isolates Hoku 1 and HN02-4101, The genotypes of F2 individuals were deduced based on the reactions of F3 lines to rice blast isolates. Molecular mapping of resistance genes were conducted using SSR markers. The gene of HKZJ resistance to rice blast strain Hoku 1, Pi-hkl(t), was mapped on chromosome 11, linked to marker RM7654 and RM7212 with a distance of 7.2cM and 18.7cM respectively. Another R gene of HKZJ resistance to isolate HN02-4101, Pi-hkl(t), was mapped on chromosome 12, linked to marker RM277 with a distance of 10.5cM. The R gene of Tieganqing to rice blast strain Hoku 1, Pi-tgl(t),was primarily mapped on chromosome 8, linked to RM308 with a distance of 17.6cM. It is necessary to test allelic of the three genes with the former mapped nearby genes resistance to rice blast to conclude whether they are new R genes.According to the published sequences of avirulence genes from rice blast fungus Magnaporthe grisea, four pairs of special primers were designed to amplify from DNA templates of 31 isolates from various regions by...