The vegetative compatibility of Magnaporthe oryzae from Taiwan

• Main Authors: Kachonsak Iamnok, 甘忠誥
• Other Authors: Chih-Li Wang
• Format: Others
• Language: en_US
• Published: 2015
• Online Access: http://ndltd.ncl.edu.tw/handle/41456046801246393087

碩士 === 國立中興大學 === 植物病理學系所 === 103 === Rice blast disease caused by Magnaporthe oryzae (Anamorph: Pyricularia oryzae) is a serious disease that reduces rice production worldwide. Vegetative compatibility has been used to demonstrate the genetic diversity, and thought as an important mechanism contributing genetic exchange within and between populations of ascomycetousfungi. In order to assess the vegetative compatibility of M. oryzae populations in Taiwan, agar plugs of 87 isolates were placed on minimal media (MM medium) amended with 60 g/L of potassium chlorate to recover nitrate non- utilizing (nit) mutants. The fast growing colonies, the phenotype of nit mutants on MM medium, were obtained from 17 % of agar plugs of all isolates and 71.04 % of them were real nit mutants. Phenotypic classes of nit mutants were determined by growth patterns on media which contained one of four nitrogen sources (sodium nitrate, sodium nitrite, hypoxanthine and ammonium), and were assigned as nit1, nit3, nitM or nitA. In this study, four phenotypic classes of nit mutants were recovered with unequal proportions: nitA (31.41%), nit1 (27.6%), nit3 (24.01%), and nitM (17.41%). Sulfate non-utilizing (sul) mutants were also recovered from 1176 agar plugs of 53 isolates which showed no complementation between their nit mutants. The fast growing colonies were derived from 37.5% of transferred agar plugs, and 50.34 % of them were real sul mutants. A peculiar high percentage (35.19 %) of heterokaryon self-incompatible (HSI) isolates was determined by no complementation in pairings of their nit / nit mutants and nit / sul mutants. To study the population structure of the 86 isolates, isolate 63 (a heterokaryon self-compatible isolate ) was used to be a tester isolate in order to pair with other 86 isolates with all possible combinations, resulting in four types of heterokaryon formations: negative type (21.60%), weak type (15.90%), medium type (6.81%) and strong type (55.68%). Notably, among isolates that showed strong type of heterokaryon formation withisolate 63, heterokaryon formation may not occur between each other by pairing their nit mutants. Pot2 polymorphism was used to demonstrate the population structure of 23 isolates with four types of heterokaryon formation. There was no correlation between the results of heterokaryon formation and Pot2 polymorphism. This study suggested although the pot2 polymorphism of M. oryzae isolates are diverse, they may derived from a predominate VCG group.