Genetic Analysis Of Blast Resistance In Japonica Rice Landrace Tieganqing From Taihu Region

Rice blast is caused by fungus pathogen Magnaporthe grisea, which is the one of the most important destroyed rice diseases. The genetic analysis of disease resistance in rice varieties by traditional genetic analysis and SSR markers and mapping the resistant genes are very useful for breeding of rice varieties resistant to rice blast. In present study, The resistant variety Tieganqing and susceptible variety Suyunuo were selected as parents to make crosses for F2 populations. Finally, the resistant gene Pi-t1 has been mapped.1.Resistant spectra of Magnaporthe grisea in the resistant variety Tieganqing.The reaction of 12 Japanese differential varieties with a single known blast resistance gene and japanica rice landrace Tieganqing from Taihu Region, to the strains used in this experiment is researched. The results indicated that Tieganqing is highly resistant to the several Chinese races and Japanese strains of Magnaporthe grisea. Among the known blast resistance genes in the Japanese differential varieties, Pi-i, Pi-z, Pi-ta, Pi-z and Pi-t show resistant to both of ZG1 and ZE3, which are representative blast races in Taihu Region. These genes may be applied in the local blast resitance breeding program.2.Genetical analysis of blast resistant genes in the progeny populations of crosses between Tieganqing and Lijiang. The F1, F2, BCi and RILs populations from cross combination (TieganqingX Lijiang) were inoculated with two Japanese differential strains Ken54-04 and Hokul, which results indicated that the resistant variety Tieganqing has two dominant genes that condition the resistance to stain Ken54-04, and one dominant gene that conditions the resistance to strain Hokul. F1, F2and BC1 from crosses of Tieganqing and Lijiang are inoculated by two races ZG1 and ZE3. Results showed that the resistance in the resistant variety Tieganqing to the two races was respectively controlled by one dominant gene. By means of Cumulative Distribution Curve Method, the F3 lines derived from cross combination (Tieganqing Suyunuo) were tested with races ZG1 and ZE3 respectively. The resultes confirmed that the resistance of Tieganqing to ZG1 and ZE3 was respectively controlled by one dominant gene.3.Allelic test of the resistant gene with known genes. The F? from crosses of Tieganqing and six Japanese differential varieties were inoculated with strain Hokul.the results indicated that the resistance gene to strain Hoku.l is nonallelic with known resistance genes, it may be a novel gene, which was tentatively named Pi-ll. Tieganqing was crossed with four Japanese differential varieties with single known resistance gene, the seedlings F2 progenies were inoculated with two races ZGi and ZE3 respectively, which were nonpathogenicity to the two parents. The results indicated that the resistance genes to the two races were nonallelic with resistance genes Pi-i, Pi-z, Pi-zt, Pi-ta and Pi-t4.mapping the gene Pi-t1. DNA from, the sixteen resistance and sixteen susceptible F2 individuals in the population of Tieganqing/Suyunuo were mixed respectively, forming a resistance bulk and a susceptible bulk for screeing polymorphic markers. Using 136 SSR primer pairs screened the template DNA of two bulks,respectively, obtaining one marker RM308, which is polymorphic between the two bulks. RM308 was used to screen for parents and individuals in the F2 populations, discovering that Pi-tl was co-segregated with the marker RM308 in chromosome 8. Therefore, the gene Pi-tl was mapped on rice chromosome 8.