Archivio Journal of Plant Pathology

Abstract:

To unravel the genetic diversity of Sclerotinia sclerotiorum, 90 isolates collected from a single sunflower field in Wenquan of Xinjiang were studied using the method of mycelial compatibility grouping (MCG). Meanwhile, the oxalic acid (OA) secretion ability, polygalacturonases (PG) enzymatic activity and pathogenicity of the isolates within the same and between different MCGs were studied. The distribution of inversion minus (Inv-) and inversion plus (Inv+) isolates of S. sclerotiorum at MAT locus within the same MCGs and also in the whole population were identified using specific PCR primers. The sensitivity of S. sclerotiorum isolates to both carbendazim and dimethachlon fungicides were also tested in this study. The results suggested that the 90 isolates from a single sunflower field in Wenquan, Xinjiang region, can be grouped into 15 MCGs. MCG1, the biggest group, contained 34 isolates, representing 37.8% of all the tested isolates; 6 MCGs contained only a single isolate; 8 MCGs include 2 to 13 isolates each. The dramatically variation on OA level, PG enzyme activities and pathogenicity was observed among isolates from the same and between different MCGs, and no obvious positive correlation was detected between OA, PG and pathogenicity. For mating type distribution ratio, 17:17 (1:1) ratio of Inv+ and Inv- isolates at mating type locus (MAT) was observed only in MCG1, however, 12:1, 7:2 and 9:1 of Inv+ to Inv- ratio at MAT locus was detected in MCG2, MCG4 and MCG6, respectively. The distribution ratio of Inv+ and Inv- in the whole population is 56:34, which is deviated from the 1:1 steady state. The results of fungicide sensitivity test within MCG1 and MCG2 suggested that 84% of isolates is more sensitive to dimethachlon than to carbendazim. Seven isolates, three from MCG1 and four from MCG2, showed the opposite tendency of sensitivity to both fungicides. Three isolates, one from MCG1 and two from MCG2, showed the same sensitivity to both fungicides. Based on above results, we concluded that dramatic genetic diversity do exist within S. sclerotiorum population collected from a single sunflower field in Wenquan of Xinjiang.