The Population Structure Of Sclerotinia Sclerotiorum In Sichuan Province

To determine population structure of Sclerotinia sclerotiorum and to provide the scientific base for disease controlling and resistance breeding, sclerotia samples showing symptoms of sclerotinia stem rot from different region and hosts in Sichuan province were collected, isolated and identified in 2004-2005. The isolates representing different soures were selected to test aggressiveness, mycelial compatibility groups and soluble protein, isoesterase patterns, the results of the research showed as follows:105 strains of S.sclerotiorum isolated from different region and host in Sichuan were tested for aggressiveness on rapeseed at flowering stage. The results shown that all tested strains of S.sclerotiorum could infect rapeseed, but there were obvious differences in lesion size.These differences suggested that the strain of S.sclerotiorum had differentiation of aggressiveness and the aggressiveness of S.sclerotiorum may not relate to the geographic distribution and host origin. Study on effect of 4 inoculation methods (9 treatments) on rapeseed, 4 methods accuracy identified isolates aggressiveness. Among 4 methods, detached leaf inoculation method with mycelial plug was the most simple, rapid and accurate inoculation method for aggressiveness test of S.sclerotiorum. The position of leaf and stem had no effect on the result of aggressiveness test on rapeseed at flowering stage. The optimum temperature for aggressiveness test was 15℃~25℃.Isolates were paried in all possible combinations on Modified Patterson's medium (MPM). Among 80 isolates, 63 different Mycelial Compatibility Groups (MCGs) were distinguished, 52 of which were made up of only one strain compatible with itself and the largest group consisted of only 4 isolates. The resultes indicated that the genetic heterogeneity existed within the species. Pairing between the isolates within the same MCGs were compatible, but the reaction type were not identical to the other isolates. There was no related between the types of MCGs. and geographic distribution, host origin and aggressiveness of the tested isolates. Although PDA medium can be used for testing mycelia compatibility among strains of S. sclerotiorum, but the MP medium is the better media for testing. However, on PDA medium, a clear zone, devoid of significant mycelia growth, separated the mycelium of one isolate from the other were not observed between...