Rhamnolipid biosurfactant could be a green approach for the management of maydis leaf blight of maize

Abstract

Southern corn leaf blight or maydis leaf blight (MLB) caused by Cochliobolus heterostrophus (Drechs.) [(anamorph Bipolaris maydis (Nisikado and Miyake) Shoemaker] is an important disease of maize. Current pest management strategy relies mostly on chemical pesticides becomes a public concern due to environmental pollution. Hence use of green compounds (GRAS) has been emphasized for pest management so as to achieve sustainable agricultural productivity. Recently, biosurfactants are receiving much attention and brought in to use for plant pathogen elimination and also for increasing the bioavailability of nutrients for beneficial plant associated microbes. Biosurfactants are a diverse group of surface active molecules produced mostly on microbial cell surfaces and they can be excreted extracellularly. The present study was carried out to evaluate the efficacy of rhamnolipid (RL) biosurfactant produced by newly isolated Pseudomonas aeruginosa strain SS14 as an antifungal agent against B. maydis in Zea mays L. In vitro experiment was conducted by adopting poison food technique at different concentrations (25, 50 and 100 ppm). The studies indicated that the biosurfactant produced by this bacterial strain inhibits the growth of B. maydis by 39 per cent at a concentration of 100 ppm. In planta, treatment of maize seeds with a RL concentration of 100 mg/lit with foliar spray of 100 mg/lit resulted in improved biomass compared to those of healthy control plants and complete suppression of characteristic disease symptoms of MLB disease. The results demonstrated the possibility to develop a sustainable and eco-friendly management measure against the necrotrophic fungal pathogen B. maydis.