Biological Characteristics?Pathogenic Differentiation And Genetic Diversity Of Sclerotinia Minor On Sunflower

Sunflower Sclerotinia blight is a worldwide distributed fungal disease,which occurs in every sunflower planting area in China.The destructive disease can lead to significant losses in both sunflower yield and seed quality and seriously affects the development of the sunflower industry in China.In this study,the biological characteristics and genetic diversity of Sclerotinia sclerotiorum and Sclerotinia minor strains collected from the cities of Wulanchabu,Baotou and Hohhot in Inner Mongolia were studied.The results obtained are as follows:1.A comparative study of the biological characteristics and pathogencity differentiation of Sclerotinia sclerotiorum and Sclerotinia minor collected from the same field of Gaojiadi,Baiyinchagan Township,Wulanchabu,Inner Mongolia.We found that the average growth rate of mycelium,the secretion of oxalic acid and the activity of polygalacturonase in Sclerotinia sclerotiorum were all higher those of Sclerotinia minor.The results of pathogenicity test showed that the virulence of Sclerotinia sclerotiorum was significantly higher than Sclerotinia minor.2.Compared with 23? culture conditions,the growth rate of mycelium,the secretionof oxalic acid and the activity of polygalacturonase were obviously improved after Sclerotinia sclerotiorum and Sclerotinia minor were treated with low temperature at 4?,and the corresponding virulence was also increased.3.The mycelia compatibility group(MCG)was studied in Sclerotinia minor collected from the stems of single plant in different sunflower fields in Siziwangqi,Wulanchabu city.The results showed that the sclerotiacollected from the single plant GHC5 in Gonghecheng were divided into 4 different MCGs,the largest group included 63.3% of all the tested strains,while the sclerotia were collected from the single plant GHC4 had only two MCGs and the larger group included 80.0% of all the tested strains.4.The Sclerotinia minor,which were isolated from the two sunflower stems TX1 and TX2 collected from the same hole in Hongqitan,Siziwangqi,Wulanchabu city,were both divided into 3 MCGs.Among which the number of Sclerotinia minor strains in the largest group from TX1 and TX2 taking 86.7% and 76.7% of all the tested strains,respectively.5.According to the results of grouping the 110 Sclerotinia minor strains collected from 9 different sites in central Inner Mongolia by MCG,we found that the tested strainscould be divided into 14 MCGs.The largest group contained 32 strains,taking 29.1% of all the tested strains,five groups only contained 1 strain,taking 35.7% of all the MCGs.By comparing the biological characteristics and pathogenicity of isolates from different VCGs,we found that the growth rate of mycelium and oxalic acid secretion from different MCGs had significant difference,except for the number of sclerotinia formation,the activity of PG enzyme and the pathogenicity.However,all the indicators tested had significant difference within the group.6.The distribution of two mating type of the 110 strains was identified by using the specific primers for mating types.the results showed that the ratio of Inv-and Inv+ type was 1:1 in MCG2,the 1:1 ratio of Inv-and Inv+ type was only observed in MCG2,while the ratio of Inv-and Inv+ type in other MCGs were all deviated from 1:1 and Inv-was the dominant mating type.