Efficacy and mode of actions of biocontrol agents against Alternaria alternata causing leaf blight disease in Anthurium

For the eco-friendly management of the Alternaria leaf blight disease, bacterial and fungal biocontrol agents isolated from the rhizosphere of Anthurium were compared for their efficacy based on the mechanisms of biocontrol. The effective isolates were formulated and tested against leaf blight of anthurium. Seven isolates of fluorescent pseudomonads, 6 isolates of Bacillus spp. and 4 isolates of Trichoderma viride was tested against Alternaria alternata. Among the biocontrol agents tested, isolates Pf1, BsM3 and Tv2 was found to be highly antagonistic to A. alternata in vitro. Among 13 isolates, Pf1, BsM3 and Tv2 showed the strongest in vitro antagonism. Molecular characterisation confirmed the identity of rhizobacterial isolates. Isolates of Pseudomonas fluorescens, Bacillus subtilis and T. viride produced siderophore in vitro. The isolates CFP1 and Pf1 were found to produce salicylic acid (SA), indole-3 acetic acid (IAA) and ammonia. In pot and field experiments, soil application of coir pith-vermicompost formulation of Pf1 (250 g/plant) followed by 3 foliar sprays of the liquid formulation (0.2 %) reduced disease severity by approximately 55 % (pot culture) and 48 % (field) relative to the control. The results demonstrate the potential of Pf1-based formulations as effective and eco-friendly options for managing Alternaria leaf blight in Anthurium.