High genetic diversity and aggressiveness of Sclerotinia sclerotiorum in soybean (Glycine max) in central Brazil region

Abstract

The diversity and aggressiveness inter- and intrapopulation of Sclerotinia sclerotiorum through mycelial compatibility groups and the evaluation of representative isolates of these groups were investigated for the disease severity in soybean plants. The isolates were derived from sclerotia collected in different soybean-producing regions of Central Brazil. For each location, mycelial compatibility analyses were conducted in a completely randomized design with two replications and 25 isolates. After the intrapopulation, interpopulation analyses were carried out, with a total of 31 isolates, using one or two representative isolates of each mycelial compatibility group of the intrapopulation analysis. For assessing isolates aggressiveness, the petioles of soybean cultivars M-SOY 7908 RR and BRSGO 7760 RR were inoculated with 21 representative isolates of mycelial compatibility. The length of lesions on the stem was measured three and seven days after inoculation. The experiment was arranged in a completely randomized factorial design, testing 21 (isolates) × 2 (cultivars), with 3 replications. In intrapopulation analyses, the genetic diversity of S. sclerotiorum was low, with at most three compatibility groups per population. In the interpopulation analyses, eight compatibility groups were detected, of which one with 19 isolates was predominant. The isolates differed significantly inaggressiveness on both the cultivars. M-SOY 7908 RR was found to be the most susceptible cultivar and SSSM25 the most aggressive isolate.