Effect of Cell-free Culture Filtrates of Bio-control Agents on the Spore Germination and Infection by Phytophthora Infestans Causing Late Blight of Potato

Potato ranks fourth as the most important food crop in the world. The crop is known to suffer from many diseases among which late blight is more devastating. Therefore, culture filtrates of bio-control agents, (Trichoderma virens, Trichoderma viride, Paecilomyces lilacinus and Pseudomonas fluorescens) were tested for their effectiveness on the spore germination and infection in-vitro, as fungicides usage leads to more production cost, besides development of fungicide resistance. Trichoderma virens, Trichoderma viride and Pseudomonas fluorescens culture filtrates showed no spore germination at all the dilution ratios of culture filtrate (CF) and sterile distilled water (SDW) after 48 hours of incubation. In detached leaf assay for infection studies T. virens, T. viride and P. fluorescens culture filtrates inhibited infection by P. infestans at all the dilution ratios. Trichoderma virens culture filtrate completely inhibited infection in green house grown potato plants. T. viride culture filtrate showed 45% of the plant infection.