Synergistic effect of oilseed cake and biocontrol agent in the suppression of Fusarium wilt in Solanum lycopersicum

The antagonistic efficacy of a biocontrol agent in combination with oilseed cake against fungal phytopathogens has been sparsely explored. The present study aimed to evaluate the antifungal activity of a biocontrol agent (Trichoderma harzianum MTCC 3928) formulated with oilseed cake (OSC) against Fusarium oxysporum f. sp. lycopersici responsible for causing vascular wilt in Solanum lycopersicum. In in vitro studies, OSC of mustard (Brassica juncea) exhibited significant mycelial inhibition against the pathogen. The volatile plate assay showed mycelial inhibition of 70 and 40% with unautoclaved and autoclaved mustard cakes, respectively. The aqueous extract (10% v/v) of the mustard cake was the most effective with 47.3% mycelial inhibition of pathogen over control. In addition, volatiles and aqueous extract of mustard cake subjected to GC-MS analysis revealed a range of antifungal bioactive compounds with hexanedioic acid, dioctyl ester (16.57%), and oleic acid trimethylsilyl ester (12.41%) being predominant compounds. In in vitro studies, it was noticed that the T. harzianum strain was compatible with mustard cake, and hence used as a growth substrate for its mass multiplication. SEM analysis revealed no distortion in spores and mycelium of T. harzianum grown on the mustard cake. Further, seed germination assay suggested the optimum concentration of mustard cake (10%) supporting the germination rate and economics of formulation development. In in planta assay, the combination of biocontrol agent and mustard cake showed 48% disease reduction, and ~ 40% with T. harzianum alone in comparison to untreated control. Also, the combination of mustard cake and T. harzianum significantly enhanced the growth parameters of S. lycopersicum. The findings of the current study identified an environmentally friendly alternative for mitigation of Fusarium wilt, thereby providing a sustainable option for mitigation of wilt disease and enhancement of plant health.