Microbial detoxification of pathotoxin produced by spot blotch pathogen Bipolaris sorokiniana infecting wheat
2011
Aggarwal, Rashmi | Gupta, Sangeeta | Singh, V. B. | Śarmā, Sapanā
Bipolaris sorokiniana causes spot blotch in wheat and barley. The pathogen produces toxin (BS-toxin), which is a sesquiterpenoid belonging to eremophilane family. Isolates of Trichoderma spp., Chaetomium globosum and Pseudomonas fluorescens were tested for detoxification of BS-toxin amended in semi-synthetic medium at different concentrations. All the antagonists showed mycelial growth in toxin amended medium but their growth was less in comparison to growth in normal medium. The growth of biocontrol agents decreased with increasing concentration of toxin. Two isolates of C. globosum (Cg1 and Cg2), T.viride (TV5-2) and Pseudomonas fluorescens produced 4.9, 2.9, 3.6 g mycelium and 5.5 × 105 cfu /ml, respectively exhibiting 50% or less reduction in growth in BS-toxin amended medium at 1,000 ppm concentration. The biocontrol agents also reduced the severity of toxin-induced symptoms and electrolyte leakage from the wheat leaf tissues. Among the microbes tested, maximum reduction in electrolyte leakage was observed in C. globosum (Cg2) treated toxin samples. The spectral analysis also showed a remarkable decrease in optical density of Cg2 treated toxin at 294 nm. High Performance Liquid Chromatography (HPLC) analysis showed almost complete degradation of BS-toxin in C. globosum (Cg2) treated samples.
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