In vitro response of one isolate of Rhizoctonia solani, the pathogen of the rice sheath blight and four isolates of Trichoderma to glyphosate
Rhizoctonia solani Kuhn is the causal agent ofthe sheathblight of rice (Orysa saliva L.), one of the most importantrice diseases in Colombia. G1yphosate (N-phosphonomethylglicine acid) is sprayed in rice fields as a preplant herbicide, specially aimed at red rice (O. saliva). Preliminary field observations in Tolima, Colombia suggested a relationship between intensive use of glyphosate and sheath blight incidence. Thus, the present study was undertaken to shed light on the effect of glyphosate on R. solani and Thrichoderma sp., a.putative antagonist, under laboratory conditions. The effect of the herbicide was assessed on the growth ofR. solani in summerged culture and solid media and of Thrichoderma on solid media. R. sotaní withstood up to 300 mg L-! without expressing reduction in growth, Increasing concentrations of the herbicide caused growth reduction, and the detrimental effect reached a plateau at 2500 mg L-1. Rhizoctonia growth was not enhanced at any herbicide concentration. The expected concentration of glyphosate in the soil after spraying at commercial dosages would be O, 75 mg Kg', which is well below the observed in vitro threshold. The response of Thrichoderma was similar to that of R. sotaní. Glyphosate did not affect the antagonistic ability of Thrichoderma against R. solani. These results do not support the view that glyphosate, as an herbicide treatment in ricefield, may affect in any way the population densities of R.sotaní or its antagonist Thrichoderma sp. Therefore, thepostulated connection between intensive herbicide useand increased sheath blight incidence is not substantiatedon mycelial growth alone. This relationship should beexplored in terms of selerotial survival and germination.
| Main Authors: | , , |
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| Format: | Digital revista |
| Language: | spa |
| Published: |
Universidad Nacional de Colombia - Sede Bogotá - Facultad de Ciencias Agrarias
2002
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| Online Access: | https://revistas.unal.edu.co/index.php/agrocol/article/view/21879 |
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