Evaluation of environmental factors for optimum growth of Rhizoctonia solani causing root rot of cluster bean (Cyamopsis tetragonoloba)

Abstract

Clusterbean [Cyamopsis tetragonoloba L.) Taub.] is popularly known as “Guar” or “Guwar” and belongs to family Fabaceae of kingdom Plantae. It is an important legume crop and mainly grown under rainfed conditions of arid and semi arid regions of tropical India during Kharif and Zaid seasons. It is tolerant to drought, deep rooted and can be grown for different purposes viz., vegetable, green fodder, green manuring, production of seed and for endospermic gum (30-35 percent). Root rot caused by Rhizoctonia solani is an important and becoming severe problem of clusterbean in Rajasthan as well as India under the changing scenario of climate. This study was undertaken to find the most favorable and critical point of temperature, relative humidity and pH factors for optimum growth of the Rhizoctonia solani that may help in survival, spread and cause infection in healthy hosts. The most favorable temperature for flourishing and mycotic growth of Rhizoctonia solani was 30 0C (90.00 mm) followed by 25 0C (80.25 mm). Among various level of relative humidity, 90 per cent relative humidity was most favorable for maximizing growth (90.00 mm) while 6.5 pH was highly suited for maximum growth of the pathogen (632 mg dry mycelial weight). Conclusively, this pathogen requires higher temperature for fast multiplication that is prevalent in arid region of Rajasthan and due to these favorable factors this disease may be gaining importance day by day.