Sclerotium rolfsii mycelial profile analysis by MALDI-TOF related to biological control, volatile organic compounds diversity and onion growth promotion, as influenced by Trichoderma spp.

Abstract

Trichoderma spp. have assumed an important role in promoting plant growth and controlling diseases, especially those caused by soil fungi that produce sclerotia as survival structures, including Sclerotium rolfsii. The objective of this study was to identify molecular ion alterations in the mycelium of S. rolfsii CEN216 as effected by the antagonism of seven Trichoderma strains, in addition to detecting the diversity of volatiles organics compounds emitted and the ability of these lines to promote the growth of onion plants. Trichoderma azevedoi (CEN1241 and CEN1242 strains) showed the best results regarding the mycelial growth inhibition and the ability to parasitize sclerotia of S. rolfsii in soil conditions. MALDI-TOF/MS analysis of the mycelium of S. rolfsii CEN216, after dual culture and double plate with Trichoderma spp., showed differences in the molecular ion profile when compared to the control treatment mycelium. Chemical analysis detected 49 VOCs produced by Trichoderma spp., covering six major chemical classes: alcohols, aldehydes, aromatics, hydrocarbons, ketones, and terpenes. The qualitative analysis showed that the strain CEN1241 presents greater VOCs diversity than the others, emitting 38 different VOCs. The strains T. azevedoi CEN1241, T.koningiopsis CEN1513, and T.asperelloides CEN1559 were superior in promoting seedling growth and increasing the weight of onion bulbs. Notably, in this work, it was found that strains behavior is very divergent regarding their antagonistic action to the pathogen and the promotion of growth. This reinforces the need for studies to formulate commercial products that contain more than one strain, to enable the combination of different mechanisms of action of the biocontrol agent.