No abstract

Fusarium verticillioides is an insidious fungal pathogen of maize associated with diseases such as ear rot and kernel rot. It attacks the phyllosphere region of the maize plant especially on inflorescence and cobs. Thus, this study was conducted to isolate potential phyllosphere colonizing antagonistic microbes for the management of Fusarium ear rot. Four phyllosphere colonizing antagonistic bacteria were found to be effective in suppression of the growth of Fusarium verticillioides. Based on 16S rDNA analysis, these bacterial isolates were identified as Pseudomonas aeruginosa isolate 1, P. aeruginosa isolate 2, Bacillus subtilis isolate and B. amyloliquefaciens. Among these four phyllosphere bacteria tested against F. verticillioides, the maximum inhibition of mycelial growth of F. verticillioides and production of volatile compounds was exhibited by P. aeruginosa isolate 1. Application of P. aeruginosa isolate-1, as seed treatment @ 10 g/kg of seeds, soil application @ 5 g/pot and foliar spray @ 0.2 per cent, recorded the minimum PDI with the maximum disease reduction over control. Thus, the present study showed that P. aeruginosa isolated from agricultural ecosystem could be a potential phyllosphere antagonistic bacterium for the management of maize ear rot disease.

Gliotoxin is a potent antibiotic showing antifungal activity against various phytopathogenic fungi. It is produced by Q strains of Trichoderma virens and gliotoxin non-producing strains of T. virens are designated as P strains. There is no detailed study on effect of gliotoxin on suppression of damping off of tomato caused by Pythium aphanidermatum and its phytotoxicity effect on tomato plants. Thus, the present study was carried out to assess the effect of gliotoxin on inhibition of mycelial growth of P. aphanidermatum, its phytotoxicity effect on tomato and its role on the suppression of damping off of tomato. Culture filtrates of Q strains of T. virens containing gliotoxin highly inhibited the mycelial growth of P. aphanidermatum compared to that of P strains of T. virens. Purified gliotoxin but not bis-thiomethyl gliotoxin effectively inhibited the mycelial growth of P. aphanidermatum. Tomato seeds treated with purified gliotoxin did not inhibit the germination of seeds, its root and shoot length even at higher concentration that is at 1000 ppm (fivefold inhibitory concentration against P. aphanidermatum). Foliar spray of gliotoxin on tomato plants did not show any phytotoxic effect at lower concentration but showed scorching effect at higher concentration. Seed treatment with gliotoxin producing Q strains of T. virens showed greater suppression of damping-off tomato compared to P strains of T. virens. This study clearly showed that gliotoxin producing T. virens could be used in suppression of damping-off disease incidence in tomato.