Biological Control of Pythium Damping-Off of Cauliflower by Trichoderma harzianum
Out of eight antagonists, one isolate of Trichoderma harzianum exhibited fastest growth rate and strong antagonism against Pythium apanidermaium in vitro. The prinicpal mechanism of antagonism was direct parasitization of Trichoderma by coiling around the hyphae of Pythium leading to digestion of protoplasmic contents and lysis. Occasional presence of Trichoderma in the lumen of Pythium hyphae was also recorded. Soil application of wheat bran saw dust (WBSD) preparation of Trichoderma gave 32.4 to 77.0 percent control of damping-off under glass house conditions. Seed coating with Trichoderma (1.6 × 1010 spores/ml) resulted in 31% control of the disease. WBSD preparation of T. harzianum; either live or killed, promoted the growth and vigour of cauliflower seedlings. Apron at 5 and Thiram at 100 μg/ml proved better and completely inhibited the radial growth of P. ahpanidermatum in vitro. None of the fungicides was found inhibitory to T. harzian am except Thiram. Seed treatement with Apron, Fytolan, SAN 506 F and Thiram gave 15.7 to 85.8% disease control. Integration of fungicidal seed treatment with soil application of T. harzianum resulted in 66.4% to 90% control of damping-off. Colony forming units of Trichoderma and Pythium monitored on selective media revealed that the population of Trichoderma remained almost stable where it was applied at higher rates but declined with time in lower rates of application. On the other hand, the population of Pythium declined in Trichoderma amended soil.
Biocontrol, Damping-Off, Cauliflower, Pythium, Trichoderma.
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