Investigation of the effect of heating, vesicular arbuscular mycorrhiza and thermophilic fungus on cotton wilt disease.

In this study, combinations of spores of a thermophilic fungus (Talaromyces flavus), Vesicular Arbuscular Mycorrhiza (VAM) and microsclerotia of Verticillium dahliae under various temperature treatment (31-38 degrees C) in triplicate trial, were investigated and results were compared with those of non-treated controls. Five cotton seeds were planted in each pot containing 3 kg of pasteurized soil. In each pot, combinations of 4x10(3) VAM spores, 2.5x10(9) spores of thermophilic fungus (T. flavus) and 5x10(5) microsclerotia of V. dahliae were added. Symptoms of Verticillium wilt were observed after 45 days. Index of disease severity was measured. Results indicated that pre-heating of microsclerotia at 31 and 35 degrees C for 10 and 14 h, respectively, caused a 15% reduction in leaf infection index. Presence of VAM and thermophilic fungus (T. flavus) spores caused 23 and 50% reductions in the disease development, respectively. Concurrent presence of mycorrhiza and thermophilic fungus spores caused a 10-20% reduction in disease development. These findings provide a promising approach to the control of Verticillium wilt of cotton. However, heat treatment of soil may prove difficult. Further studies in this regard are required and useful agricultural practices such as seasonal heating may be applied in the cotton fields.