Characterization of the Mycelial Compatibility Groups and Mating Type Alleles in Populations of Sclerotinia minor in Central China.

Abstract

Ninety-five single-sclerotium isolates were obtained from lettuce and weeds in three counties in central China. They were identified belonging to Sclerotinia minor based on colony morphology and the S. minor-specific DNA marker. Mycelial compatibility groups (MCGs) and the mating type (MAT) alleles in these isolates were determined using the methods of paired cultures and specific PCR, respectively, and the MCG data were used to calculate Shannon's H index (H) and Simpson index (S), thereby evaluating diversity of S. minor. Eight MCGs (MCG1 to MCG8) and two MAT alleles (Inv+, Inv-) were identified in these isolates. Low diversity was detected for the total 95 isolates (H = 1.748, S = 0.786). Isolates of different MCGs or with different MAT alleles did not significantly differ (P > 0.05) in mycelial growth rate on potato dextrose agar (PDA, 20°C) or lesion diameter on lettuce leaves (20°C), but slightly differed in the number of sclerotia produced on PDA (20°C). Furthermore, this study reported five new host plants of S. minor in China, including Capsella bursa-pastoris, Oenanthe javanica, Fragaria gracilis, Ranunculus ternatus, and Salvia plebeia, and identified three hypovirulent isolates. These results broaden our understanding about the population biology of S. minor.