Physiological Differentiation And Genetic Diversity In Sexual Hybridization Progenies Of Setosphaeria Turcica

Northern corn leaf blight is one of the important diseases in maize. The pathogen, Setosphaeria turcica, is heterothallic. It is predicted that the plant fungal pathogen can enhance its pathogenicity, change its pathogenic host range and generate new physiological races through sexual hybridization. Therefore, two parent isolates, 132 and 135, belonging to two opposite mating types and different races were chosen to study the pathogenic differentiation and genetic diversity in their progenies.Both parent isolates and their seventy progenies which belonging to which physiological races of S. turcica was identified using identification hosts. The results showed that the parent isolate 132 belonged to race 23N and the other parent isolate 135 belonged to race 23. About 41.1 percent and 20 percent progeny isolates were identified to be race 23N and race 23, respectively, but race 0, 1, 2, 3, 13, 123, 12N, 13N and 123N were also existed in these isolates tested. Race 123N, a pathogenic race to corn with all the known four resistant genes, should be paid more attention. The physiological differentiation in progeny isolates is diversity and broad.The fingerprinting analysis based on AFLP molecular marker was carried out and an effective AFLP technological system which was suitable for genetic analysis of S. turcica had been established. The results showed that similarity coefficient between isolates tested was from 0.87 to 0.99. Most of progeny isolates were similar to their parent isolates. Moreover, there were more progenies similar to parent isolate 132 compared to isolate 135. It indicated that the genetics of S. turcica was complex. Parent isolate 132 maybe had stronger genetic transmittal ability than parent isolate 135 in the course of sexual hybridization.The esterase isozyme polymorphism among the parent isolates 132 and 135 and their progenies were analyzed by polyacrylamide gel electrophoresis (PAGE). The results showed that there was great diversity in the esterase isozyme map among parent and progenies isolates. Four common bands were found among the total nine bands on the esterase isozyme map. Their Rf values were 0.256, 0.684, 0.786 and0.923, respectively. The other five bands are specific and their Rf values were 0.111, 0.291, 0.342, 0.496 and 0.855, respectively. These bands of esterase isozyme formed into 6 different patterns of isozyme bands.Through comparing the physiological differentiation, with AFLP molecular diversity and esterase isozyme polymorphism, it was found that the physiological differentiation and AFLP molecular genetic polymorphism were not definitely completely correlated. The physiological differentiation and esterase isozyme polymorphism were not correlated to some extents either.