Genetic Diversity in Magnaporthe grisea & Pathogenic Variation of its Progeny by Hyphal Fusion
Y.Shen1. CY, Li 2 J. Manry3, C.Rojas3 XH.Zbao1, PL.Zhu1, ZX.Luo2, YL.Wang1 M.Levv3
1 China National Rice Research Institute, Hangzhou 310006. China 2 Yunnan Academy of Agricultural Sciences, Kumnin 650205, China 3 Purdue University,West Lafayette, IN 47907. USA
Background and objectives
Rice blast is one of the most widespread and destructive diseases of rice in almost all rice growing regions of China. Annual yield losses of rice are around 2-11 million tons. It has become a big obstruction to development rice production in high Yielding areas. Breeding resistant cultivar of rice is the most economic efficient for controlling the disease. To develop improved breeding strategies for control the rice blast disease. MGR-DNA fingerprinting and pathotyping were combined to determine the population structure of the pathogen and the relationship between this virulence diversity of the pathogen in China. the pathogenic variation of its progeny by hvphal fusion was studied as well.
Material and methods
The MGR-DNA fingerprints of 475 isolates in Magnaporthe grisea collected from 146 different sites among 17 provinces (cities) during 1980-1996 and other 40 isolates, including 11 parental isolates (asexual/sexual) with hyphal fusion, 22 recultural isolates of hyphal fusion spots and the 5th generational isolates of 7 paired isolates have been studied with a dispersed repetitive sequence probe MGR586/EcoR I digest combination since 1992.
Results and conclusions
The fingerprint data documents a generalized genetic organization. Forty-five pathotypes of M.grisea were distinguished into 56 separate lineages. Each lineage had a limited host range and these relationships were maintained several years over broad geographic distribution. PRC-1,2,8,10.12,15 and 16 were detected in multiple years. The two most heavily sampled provinces, Zhejiang and Sichuan, contained 19 and 24 lineages. respectively, only four of them PRC-1,8, 1 5, ind 16 were in common. The relationship between lineage stricture and virulence organization have been identified by determining the pathotypes of isolates in controlled seedling inoculations on 7 Chinese differentials and 5 near- isogenic lines. Based on the results obtained for 97 isolates from 28 lineages, a set of isolates with different virulence spectra to select suitable donors for more durable resistance breeding were obtained.
The results of fingerprinting showed that most of the isolates with hyphal fusion were distinguished into different lineages. Compared with the results of pathotype identification, we concluded that hyphal fusion is one of the important causes to pathogenic variation. being as important as sexual hybridization, heterokaryosis. and natural mutation in rice blast fungus.
1. Shen Y. Zhu PL,. Yuan XP, Manry J. Levy, M. 1996. Scientia Agrictultura Sinica. 29(4):39-46
2. Shen Y. Li CY, Yuan XP, Zhao XH, 1997. Scientia Agricultura Sinica, 30(6):16-22