Studies On Resistance To Rice Blast Disease In Chenghui 448

Rice blast, caused by Magnaporthe oryzae, is one of the most destructive diseases of rice in the world. Utilizating resistance genes and breeding resistance variety are considered as the most efficient,economic and environmentally friendly way to control the rice blast. The monitoring of the field expression and studies on the hereditary characters as well as the composition of resistance genes of the resistance to the disease are of great importance to the prediction of the disease epidemic and the breeding of the new resistant varieties.Rice restorer line Chenghui 448 of wide compatibility was bred by Crop Research Institute under Sichuan Academy of Agricultural Sciences. By spray inoculation at seedling stage, resistance spectra of Chenghui448 to the fungal strains isolated from Sichuan Province during 2002~2008 . Panicle blast of hybrid rice combination with Chenghui448 or its sibling line Chenghui177 as restore lines were investigated in blast nurseries at different location in Sichuan Provinces. A resistance gene in Chenghui 448 was primely identified by inoculating F2 population crossed by Chenghui448 as the resistant parent and CO39 as the susceptible parent.Tatally 452 blast strains collected in 2002～2008 were inoculated onto Chenghui448 ,the result indicated that the resistant frequency in 2004 was significantly lower than that in 2002 and 2003; The frequencies in 2008, compared with 2007, was again significantly decreased.The rate of panicle blast in different nurseries showed that each variety had no significant difference in field resistance expression beween Yingshan,Dazhu and Pingshan. Except D You 448,every varity was susceptible to rice blast in disease nursery at Pujiang.The blast isolate 04-6-8-2 was used to inoculate the Chenghui 448, the susceptible parent CO39 as well as their F2 progeny.The result of the X2 test of the segregation rate of the reisitant and susceptible plants in F2 Population suggested that resistance to the isolate in Chenghui 448 was controlled by a single dominant gene. 181 pairs of rice SSR primers were used to examine the polymorphism between the two parents and the results showed that the polymorphism rate was 35.57%. A blast resistance gene Pi-ch(t) in Chenghui 448 was primarily mapped at the long arm of Chromosome 11, respectively 0.3cM and 9.2cM away from SSR marker RM224and RM187 by using BSA-RCA (bulked-segregate analysis and recessive-class analysis) strategy.