Biological control of fruit-rot of jackfruit by rhizobacteria and food grade lactic acid bacteria

Abstract

Fungal species causing fruit rot of jackfruit have been isolated from seven different locations of Birbhum and Burdwan districts of West Bengal, India. Each isolate showed more or less similar microscopic characteristics. A representative strain VBAM1, isolated from a severely infected jackfruit was identified as Rhizopus stolonifer by 28S rDNA sequence homology. Increased reducing sugar content in pectin broth indicates pectinase production by the pathogen. The pathogen was not inhibited by ⩾500μg/ml of Mancozeb and Bavistin. Copper oxychloride, Blytone 50% a.i. showed antifungal activity at comparatively lower concentration (200μg/ml). Two rhizospheric bacterial strains, Burkholderia cenocepacia VBC7 and Pseudomonas poae VBK1, and three different strains of Lactococcus lactis subsp. lactis can produce significant zones of inhibition against the pathogen in dual culture overlay plates. They induced mycelia breakage of pathogen as evidenced from scanning electron micrographs. When applied to whole plants, the strains reduced or prevented disease and when applied postharvest to Rhizopus inoculated fruit delayed and/reduced disease incidence. These agents were also re-isolated from the applied surfaces and survived for long time when mixed with suitable carrier base indicating stability in a formulation over time.