Similar Aggressiveness of Phenotypically and Genotypically Distinct Isolates of Sclerotinia sclerotiorum

Understanding how Sclerotinia sclerotiorum aggressiveness varies among isolates may be useful for breeding programs aimed at developing common bean cultivars resistant to white mold. The aggressiveness of 20 S. sclerotiorum isolates collected in common bean fields from four Brazilian states was tested against two common bean genotypes (Perola and A195) using two inoculation methods. The isolates were characterized using 10 microsatellite (SSR) loci, mycelial compatibility groups (MCGs), partial sequences of the oxaloacetate acetylhydrolase (OAH) gene, and morphological traits. Twenty SSR and seven OAH haplotypes, 10 MCGs, and high variability in colony morphology were found. One isolate was more aggressive when inoculated on plants of the genotype A195, but all other isolates had similar aggressiveness. Aggressiveness was not related with MCGs, SSR, OAH haplotypes, mycelial pigmentation, growth rate, or sclerotia production.