Anaalysis Of Genetic Structure Of Sclerotinia Sclerotiorum Populations From Different Regions Of Jiangsu Province

Stem rot caused by Sclerotinia sclerotiorum is a devastating disease of rapeseed in Jiangsu province. In this study, 145 Sclerotinia sclerotiorum isolates were collected from different regions of Jiangsu province. The aggressiveness of isolates were tested. The results showed that the aggressiveness of 5. sclerotiorum isolates was significantly different, but there was no significant differences in resistance of 3 rape varieties. The aim of this study is to provide help for rape breeding and aggressive identification of isolates.The fungicide Carbendazim has been used in controlling S. sclerotiorum since 1970s. For monitoring the resistance of S. sclerotiorum to Carbendazim(MBC) at present, the sensitivity of S. sclerotiorum isolates to MBC collected from different regions was examined. The results showed that the ratio of isolates resistant to MBC was 11.19% within 145 isolates. The resistance level of these isolates was high. EC₅₀values of resistant isolates were higher than 100μg/ml. The ratios of isolates resistant to MBC were different among regions in Jiangsu. The ratio of resistant isolates reached 28.12% in the Suzhou population of S. sclerotiorum, but no resistant isolate was found in Gaochun. Theβ-tubulin gene from resistant isolates was PCR amplified and ThaI restricted. The result showed that a point mutation at amino acid 198 ofβ-tubulin gene encoded protein was detected in all resistant isolate, and results in occurrence of resistance to MBC for S. sclerotiorum.The genetic diversity and genetic structure of populations of Sclerotinia sclerotiorum(Lib.) de Bary from different regions of Jiangsu province were investigated using MCGs and the Microsatellite(SSR) method in order to provide some information on the phylogenetic taxa and breeding for resistance to sclerotinia stem rot. 17 pairs of isolates were compatibal in 145 isolate, and there were 131 MCGs, most of which consisted of only one isolate. A minimum of two and a maximum of eight unambiguously amplified bands were generated, furnishing a total of sixty-one bands ranging in size from 160 to 550 bp, corresponding to an average of 5.1 bands per primer pair. Forty-two of these sixty-one bands(68.9%) were polymorphic, the percentage of polymorphic bands for each primer pair ranging from 20% to 100%. The genetic similarity of all selected isolates was quite high. At the species level, the genetic diversity estimated by Nei's gene diversity(h) was 0.2992 and Shannon's index of diversity(I) was 0.4508. The unweighted pair-group mean analysis(UPGMA) cluster analysis showed that most isolates from the same regions were grouped in the same cluster or a close cluster. The coefficient of gene differentiation(Gst) in total populations calculated by population genetic analysis was 0.1625, which indicated that the genetic variation among populations was 16.25%. The gene flow(Nm) was 2.58, which indicated that the gene permutation and interaction among populations was relatively high.