The influence of Trichoderma brevicompactum treatment and drought on physiological parameters, abscisic acid content and signalling pathway marker gene expression in leaves and roots of tomato

Trichoderma species are widely known for their antagonistic properties, but plant growth promotion and abiotic stress tolerance have also been reported. Mechanisms of abiotic stress tolerance, such as drought in plants in interaction with Trichoderma spp., remain unclear. In this work, the results about the influence of Trichoderma brevicompactum on the physiological parameters and abscisic acid (ABA) content in leaves and roots of tomato, as well as the Trichodermamodulated plant response to drought are presented. Both in optimally watered plants and droughted plants treated with Trichoderma, the relative water content (RWC) was 17% higher than in untreated plants. Drought lowered RWC by 25% in both Trichoderma-untreated and -treated plants. Under drought conditions, the better water status of plants treated with Trichoderma is connected with lower stomatal conductance and closure of stomata. The lower increase of root ABA content in Trichoderma-treated plants that we observed could be an adaptive advantage in sense of smaller inhibition of plant growth induced by drought. Trichoderma modulation of the salicylic acid (SA) marker genes response to drought was observed in leaves. Our results suggest that signalling pathways of jasmonic acid (JA), SA and ABA are involved in response to both drought and Trichoderma. The mutual effect of the tested treatments leads to the modification of gene expression in comparison to the reaction to a single stress. The upregulation of SA marker genes in leaves and JA marker genes in the roots 2 weeks after the interaction with T. brevicompactum indicates that it could be promising biocontrol agent.