Abstract

Investigation of Sclerotinia sclerotiorum strains variability in Brazil

White mold is a common bean disease caused by the fungus Sclerotinia sclerotiorum, resulting in economic losses in Brazil and worldwide. Lack of knowledge about the population structure of the pathogen makes it difficult to control the disease. The aim of this study was to characterize strains of S. sclerotiorum obtained from experimental and commercial common bean fields in Brazil. We analyzed 50 strains of S. sclerotiorum collected at several locations in the state of Minas Gerais. The strains were characterized according to their ability and time for developing apothecia. Morphological and physiological analyses such as the mycelial growth index, colony color, the time required to form the first sclerotia on media, the number of sclerotia per plate, average sclerotium size, and sclerotium shape were performed. We determined the mycelial compatibility, conducted molecular analysis of microsatellites, and evaluated the aggressiveness of 28 strains. Most strains had the ability to form apothecia. A small group of strains showed mycelial compatibility, and the strains showed different aggressiveness levels. Overall, the population studied here demonstrated wide variability based on the morphological, physiological, and molecular traits analyzed. The average size and shape of sclerotia presented a correlation of 0.617, whereas the times required to form sclerotia and the number of sclerotia per plate showed a correlation of -0.455. The char-acterization of the pathogen population described herein will provide an important tool for promoting the development of bean cultivars resistant to white mold.

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