Screening And Evaluation Of Rice Germplasm Resources Resistant To Rice Blast (Magnaporthe Grisea)

Rice blast, caused by Magnaporthe grisea (Hebert) Barr, is one of the most devastating plant diseases, infecting rice crops all over the word. It has been proved that breeding and planting disease-resistant cultivars is the most economical and efficient means to control this disease. Screening and utilization of rice resources resistant to blast is the foundational measure to breed resistant varieties. This study focuses on rice growing area in Sichuan province, thoroughly analyzing the composition, distribution of blast fungus races ,and the rice blast resistance identification in main hybrid rice varieties, and the rice blast resistance identification in 72 rice germplasm resources from Guangdong province and 457 rice germplasm resources from our self collecting by leaf blast and panicle blast, and evaluating restoring or maintaining characteristics for 72 rice germplasm resources from Guangdong province and some of the resistant resources. Moreover, the agronomic characters of 72 rice germplasm resources from Guangdong province were observed in Sichuan province, and the competition superiority of agronomic traits and the grain quality of some combinations in 72 combinations from Yixiang A-line and Guangdong rice resources were evaluated.The result showed that the pathogen in Sichuan province were composed of 4 groups containing 24 races, in which ZA and ZB group were predominate with a frequency of 39.77% and 57.95% respectively, and ZB₁₃ was the predominate with a frequency of 22.73% and other main races were ZA₁₃ (17.05%), ZB₉ (7.95%). The composition of blast fungus races among different ecological regions such as Luzhou,Yaan and Pujiang disease nurseries were different .At present, the blast resistance of the main rice varieties in Sichuan was low. There were 19 varieties which were showed high or medium in blast resistance. The result of rice blast resistance identification indicated that 52 Guangdong and 239 rice germplasm resources were resistant to rice blast, occupied 72.2% and 52.30% respectively, with panicle neck blast of 1-3 scales. Among 72 Guangdong rice germplasm resources and 27 resistant resources, 45 Guangdong resources and 9 resistant resources had restoring character to male-infertile lines, 8 Guangdong resources and 6 resistant resources had maintaining character to male-infertile lines and 19 Guangdong resources and 3 resistant resources had restoring and maintaining character to male-infertile lines. The result of agronomic characters identification indicated that most of the 72 Guangdong rice resources belonged to medium or late mid-Indica, with low plant height, strong tiller, medium or small panicle, low seed setting, low 1000-grain weight and low grain yield per plant. The 72 Guangdong resources might be divided into 3 groups by using cluster analysis based on agronomic characters. Group I had 20 resources, with mid-panicle, 83.3% of the average seed setting. Group II had 21 resources, with big panicle, about 180 spikelets of the average spikelets per panicle. Group III had 31 resources, with small panicle, short growth period and low plant height. The 45 hybrid combinations were divided into 3 groups by using principal component analysis and cluster analysis based on competition superiority. Group I had 18 combinations, with the positive competition superiority of plant height, panicles per plant and spikelets per panicle, the negative competition superiority of the period of from sowing to heading, filled spikelets per panicle, seed setting, 1000-grain weight and grain yield per plant. Group II had 11 combinations, with the positive competition superiority of panicles per plant, spikelets per panicle, filled spikelets per panicle and grain yield per plant, the negative competition superiority of other traits. Group III had 16 combinations, with the positive competition superiority of panicles per plant and spikelets per panicle, the negative competition superiority of other traits. Among the 57 hybrid combinations, the brown rice rates of 12,20 and 18 hybrid combinations reached the first, second and third grade of the national high quality rice standards respectively. The chalky rice rates of 16, 28 and 6 hybrid combinations reached the first, second and third grade of the national high quality rice standards respectively. Finally, the strategies of improvement and utilization of these rice resistance resources were also discussed.