Abstract

                                A systematic field survey was conducted to document the wilt and nematode infestation on bitter gourd in Coimbatore district of Tamil Nadu. The higher disease severity and gall index were observed in Manakadavu village with 71.85 per cent wilt incidence and a mean gall index of 5.0. The pathogen, Fusarium solani was isolated and Koch’s postulates were proved under glasshouse conditions, where Manakadavu isolate of F. solani was found to be virulent. The morphological and molecular characterization of F. solani were also carried out. The interaction of F. solani and M. incognita on bitter gourd was studied in order to know whether the root knot nematode acts as a predisposing factor for the soil borne pathogen Fusarium and aggrevates the wilt severity. The in vitro efficacy of the biocontrol agents viz., Bacillus, Streptomyces, Pseudomonas and Trichoderma were evaluated by dual plate method where Streptomyces (BG 01) recorded a higher mycelial inhibition of 80.38 per cent over control. The organic amendment neem cake was found to be highly effective at both 5 and 10 per cent concentrations. The efficacy of the biocontrol agents and neem cake against the egg hatching and juvenile mortality of root knot nematode, Meloidogyne incognita was also assessed. The neem cake followed by Streptomyces (BG 01) and Bacillus (PG 12) were found to be effective in inhibiting egg hatching and the mortality of M. incognita. A pot culture experiment was conducted with efficient biocontrol agents and organic amendments. The results revealed that soil application of neem cake @ 5 g / pot + Streptomyces reticuli (BG 01) @ 10 ml / lit / pot + Pseudomonas fluorescens (Pf 1) @ 2g / pot + Trichoderma viride (Tv 1) @ 2 g / pot decreased the Fusarium wilt incidence and M. incognita infestation significantly. The above treatment also resulted in increased plant growth and yield parameters. The field trial revealed that the soil application of neem cake @ 250 kg ha-1 + Streptomyces reticuli (BG 01) @ 10 ml/ lit + Pseudomonas fluorescens (Pf 1) @ 2.5 kg ha-1 + Trichoderma viride (Tv 1) @ 2.5 kg ha-1 recorded a significantly lower wilt incidence of 14.4 per cent as against 42.5 per cent in the control, which was found to be 66.1 per cent reduction over control and gall index was also significantly reduced to 1.6 as against 5.0 in control. The treatment recorded a higher fruit yield of 15.40 tonnes ha-1 as against 10.75 tonnes ha-1 in control.

Key words : Bitter gourd, Fusarium, Root knot nematode, Biocontrol, Organic amendments