Studies On Diversity Of Sclerotinia Sclerotiorum In Hubei Province And Relationship Between Percentage Of Rapeseed Flowers Infected And Scleroinia Stem Rot Incidence In Field

Sclerotinia sclerotiorum is an important plant pathogen with worldwide distribution, the sclerotinia stem rot on rapeseed caused by it, is the most serious diseases on rapeseed in China, caused serious yield losses to rapeseed production.The biological characteristics and genetic diversity of the S. sclerotiorum strains collected from different geographical and host source in Hubei province were studied; at the same time the percentage of infected flowers at different blossoming stage of rapeseed in field was detected using molecular techniques, the correlation analysis had been taken among the disease incidence, infection rates of oilseed rape flowers and number of apothecia in different blossom stages.In 2013, 153 isolates were obtained from nine hosts in 12 districts of 7 cities. Total of 103 isolates which were from different hosts and locations were selected and analyzed for phenotypic diversity using five phenotypic traits(sclerotia production, oxalic acid production, growth rate, colony color and virulence). The isolates exhibited signi?cant differences in growth rate, sclerotia production on PDA and the virulence test on the leaves of Nicotiana benthamiana. The mean growth rate is 20.9mm/day, mean dry weight of sclerotia in one dish is 0.27g/dish. The isolates showed three colony colors(23% beige, 10% dark and 67% white). The oxalic acid production signi?cant correlated with growth rate. In this study, we inoculated the leaves of Nicotiana benthamiana for virulence test and the mean diameter on the leaves is 28.6mm. The isolates selected from 9 hosts were inoculated on the leaves of 9 hosts, no apparent relationship among the virulence and their hosts was detected.Out of 103 isolates collected, 96 isolates which were from different hosts and locations were selected and analyzed for genetic diversity in terms of mycelial compatibility groups(MCGs). 71 MCGs were found among the 96 isolates, 17 MCGs include two or more isolates, the other 54 MCGs only have one isolate. Furthmore, eight SSR primers had been used in the genetic diversity study of the 96 strains, the eight primers all have diversity, 43 bands were obtained, their sizes is between 152 bp and 385 bp. System evolutionary tree was builded based on the Nei’s genetic distance of the strain groups from different places and hosts, it showed that the genetic distance between these groups has no apparent relationship among the geographical distance and genetic relationship of host. Powermaker software was used to cluster all the 96 strains based on the Nei’s genetic distance, the cluster showed abundant genetic diversity among the isolates, these strains were divided into several groups. Moreover, STRUCTURE software was used in the structure anlysis of the 96 strains, the strains were divided into two groups.In 2013、2014, we used the nested- PCR to detect the percentage of infected flowers in cotton-oilseed rape fields and rice-oilseed rape fields in Huangzhou and Wuxue. Test results showed that the trends of the percentage of infected flowers were similar of the two kinds of rapeseed fields in two areas: begin to increase gradually from early flowering season, reach the top in full-bloom stage, and then decrease gradually. The infection rates of cotton-oilseed rape fields were always higher than that in rice-oilseed rape fields in the two areas. And significant correlation among the disease incidence, infection rates of oilseed rape flowers and number of apothecia in different blossom stages was also found in this study.