Colony Age of Trichoderma azevedoi Alters the Profile of Volatile Organic Compounds and Ability to Suppress Sclerotinia sclerotiorum in Bean Plants

Abstract

Common bean (<i>Phaseolus vulgaris</i> L.) is one of the most important crops in human food production. The occurrence of diseases, such as white mold, caused by <i>Sclerotinia sclerotiorum</i> can limit the production of this legume. The use of <i>Trichoderma</i> has become an important strategy in the suppression of this disease. The aim of the present study was to evaluate the effect of volatile organic compounds (VOCs) emitted by <i>Trichoderma azevedoi</i> CEN1241 in five different growth periods on the severity of white mold in common bean. The <i>in vitro</i> assays were carried out in double-plate and split-plate, and the <i>in vivo</i> assays, through the exposure of the mycelia of <i>S. sclerotiorum</i> to the VOCs of <i>T. azevedoi</i> CEN1241 and subsequent inoculation in bean plants. Chemical analysis by gas chromatography coupled to mass spectrometry detected 37 VOCs produced by <i>T. azevedoi</i> CEN1241, covering six major chemical classes. The profile of VOCs produced by <i>T. azevedoi</i> CEN1241 varied according to colony age and was shown to be related to the ability of the biocontrol agent to suppress <i>S. sclerotiorum</i>. <i>T. azevedoi</i> CEN1241 VOCs reduced the size of <i>S. sclerotiorum</i> lesions on bean fragments <i>in vitro</i> and reduced disease severity in a greenhouse. This study demonstrated in a more applied way that the mechanism of antibiosis through the production of volatile compounds exerted by <i>Trichoderma</i> can complement other mechanisms, such as parasitism and competition, thus contributing to a better efficiency in the control of white mold in bean plants.