Control of collar rot and root-knot of cowpea with VA mycorrhizae
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Date
1993
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Department of Plant Pathology, College of Agriculture, Vellayani
Abstract
The objective of the present study was to evaluate VA mycorrhizae as a biocontrol agent against collar rot caused by Rhizoctonia solani and root-knot nematode Meloidogyneincognita in cowpea. Three different pot culture experiments were conducted. The first two were conducted to assess the effectiveness of VA mycorrhizal fungi viz. Glomus fasciculatum, G. mosseae and Acaulospora morroweae to suppress the pathogen R. solani and the nematode M. incognita. The results of the first two experiments revealed that G. fasciculatum is the best VA mycorrhizal fungus in terms of reducing the disease intensity (collar rot) and nematode population. Artificial inoculation with VA mycorrhizae significantly increased mycorrhizal colonization, nodulation, fresh weight, dry weight, plant height and leaf number of plants. A. morroweae was found to be a comparatively weaker symbiont in terms of increasing growth and suppressing the pathogens. Based on these results G. fasciculatum was used for further studies. Analysis of total phenols was done under conditions of interaction of G. fasciculatum, R. solani and M. incognita. Plants inoculated with VA mycorrhiza always showed a higher phenol content compared with the plants not inoculated with mycorrhiza. There was a significant positive correlation between mycorrhizal colonization and phenol content of plant tissue. Hence, the VA mycorrhizal mediated disease tolerance could be attributed to the enhanced phenol accumulation. The present investigation reveals that VA mycorrhizal technology has much potential as a biological tool for the management of root pathogens of cowpea. However, for practical application, the appropriate organism, for the host/environment should be chosen.
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