Genetic Diversity In Mgnaporthe Grisea From Rice In China

Rice blast disease caused by Magnaporthe grisea (synonym: Pyricularia grisea) is one of disastrous diseases in rice. Because of pathogenic differentiation of M.grisea, resistance of rice varieties with high resistance is easily overcome in 2-3 years. So it is very important to research genetic diversity in rice blast fungus for monitoring rules regulating its variation and instructing breeding and application of resistance rice varieties.Through Pot2-rep-PCR fingerprint analysis of M.grisea isolates, haplotype code formula was devised basis of position of every amplified DNA band close to some reference bands with appearance of the most frequency. 537 tested isolates from rice from some rice-growing regions in China was divided into 2 groups. CN has 6 reference bands that tested isolates is from Jiangsu, Zhejiang and some regions in northern China; CS has 7 reference bands that tested isolates is from some regions in southern China. The DNA fingerprint haplotype code formula make it possible that researchers exchange between data from different origins.324 M. grisea isolates from rice collected from some regions in China were analyzed using rep-PCR for genetic diversity. The results demonstrated that rice blast fungus was very heterogeneous and extremely variable at DNA level. In 20 genetic lineages of M. grisea, CL20 is dominant lineage in China. Analysis of lineages distribution of rice blast fungus showed that haplotypes and lineages were different in different districts. All isolates were divided 2 groups by DNA fingerprints. CN stand for M.grisea from Jiangsu, Zhejiang and southern China; CS stand for isolates from Guangdong ,Sichuan ,etc. Result showed that variation of M. grisea from rice in China is related with varieties distribution and climate condition, etc.242 M.grisea isolates collection from rice in Jiangsu in 2000-2001, different original places were analyzed using rep-PCR. In 17 genetic lineages of M.grisea, JSL17 is dominant lineages in Jiangsu. Results showed that variation of M.grisea lineages from rice in Jiangsu was obvious from 2000 to 2001. Distribution of M.grisea lineages had some differences in different rice-growing regions of Jiangsu. Varieties are main in the effect causes indifferentials of M.grisea.230 M.grisea isolates collection from rice in Jiangsu were analyzed in pathogenicity by different DVs. They belonged to 7 physiological groups and races Gl is dominant. They produced 114 or 30 reaction types respectively on the mono-resistance-gene differential varieties from Japan or one LTH near isogenic(NILs). Analysis of the isolates for pathogencity demonstrator that many differences in pathogenicity exist in tested isolates. LTH NILs is better than other two differential varieties for M.grisea from rice in Jiangsu . Result revealed that the genetic variation by rep-PCR DNA fingerprinting method was probably independent to that detected by differential varieties and there was no direct relationship between them.