Bioefficacy of Trichoderma spp. in controlling root rot of cotton caused by rhizoctonia solani kühn
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Date
2007
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Publisher
CCSHAU
Abstract
Root rot of cotton (Gossypium spp.) caused by Rhizoctonia solani Kühn
is one of the most serious disease in irrigated areas of Punjab and Haryana.
In the present investigations an effort was made to screen local isolates of
Trichoderma spp. against R. solani and their integration with fungicides
Bavistin and Emisan and herbicides Trifluralin and Stomp in controlling root
rot of cotton under screen house conditions. Seven isolates of Trichoderma
spp. were evaluated against R. solani in vitro. In dual culture, T. harzianum-I
was most effective as it caused maximum growth inhibition (75.37%) of the
pathogen. In culture, T.viride-IV produced maximum amount of volatile
metabolites whereas T.viride-III produced maximum amount of non- volatile
metabolites. Mycelial growth rate of Trichoderma spp. was not correlated with
the amount of metabolite produced. During interaction studies the intensecoiling of T. harzianum and sparse coiling of T. viride around R. solani hyphae
were observed. Dissolution of protoplasmic content of R. solani hyphae by all
the Trichoderma spp. was also observed. Complete lysis and distortion of R.
solani hyphae was shown by T. virens. All the seven isolates and pathogen
were screened for their compatibility with three fungicides Bavistin, Emisan
and Copper oxychloride and two herbicides Trifluralin and Stomp under in
vitro conditions. Among the three fungicides Bavistin had more toxic effect on
Trichoderma spp. than pathogen R.solani. While Emisan and Copper
oxychloride caused more inhibition to pathogen than antagonists. At higher
concentration (500 g a.i/ml) all the three fungicides completely inhibited the
growth of pathogen as well as antagonists. The herbicides Trifluralin and
Stomp had greater impact on growth of R.solani than Trichoderma spp. Seven
isolates of Trichoderma spp. were evaluated as seed and soil treatment in
controlling root rot of cotton caused by R. solani under green house
conditions during summer and rainy season. Soil treatment with antagonists
was better than seed treatment. T.viride-II was most effective among all the
isolates in controlling the disease. Therefore, it was used in integrated
disease management studies. Three different talc based formulations of
T.viride-II were prepared, tested and compared with their respective fresh
cultures in controlling the disease. Pellets formulation gave maximum disease
control than others. However, fresh cultures were more effective than
formulated products. Integration of T.viride-II with half the recommended
dose of Bavistin and Emisan gave maximum disease control i.e 78.59 and
71.53 per cent respectively. In integration, Trifluralin reduced the disease
controlling efficacy of Trichoderma and also reduced the seedling length of
cotton. Stomp had no adverse effect on Trichoderma and cotton plants.
Description
Keywords
Trichoderma viride, T. harzianum, T. virens, Rhizoctonia solani, Cotton, Root rot, Biocontrol, Mechanism, Integrated disease management, Stomp, Trifluralin, Bavistin, Emisan, Formulation, Seedling mortality