Optimal Trichoderma strains for control of stem canker of brassicas: molecular basis of biocontrol properties and azole resistance

Abstract

Genus Trichoderma contains the most powerful agents used in biocontrol. Our study demonstrated that T. harzianum, T. hamatum and T. longibrachiatum can effectively control phytopathogenic fungi Leptosphaeria maculans and L. biglobosa. The effects of Trichoderma on pathogens’ growth (in dual cultures on agar media) and on disease severity (on seedlings in controlled conditions) were also confirmed by field experiments. Additionally, spraying with conidiospores in the autumn was helpful in reducing the incidence and severity of phoma leaf spots. It has also accelerated the degradation of plant stubble and the decomposition of pathogens’ fruiting bodies. Furthermore, all Trichoderma isolates showed higher cellulolytic activity and enhanced resistance to flusilazole treatments as compared to Leptosphaeria spp., which coincided with upregulation of 14α-sterol demethylases and an AbcG5 transporter. The effects we observed justify the use of Trichoderma to enhance the resistance of oilseed rape against pathogens, which in turn may lead to a decrease in the use of pesticides.