Pathogenic behaviour of leguminous isolates of Rhizoctonia solani collected from different Indian agro-ecological regions

Abstract

Pathogenic behaviour of 368 isolates of Rhizoctonia solani representing seven anastomosis groups collected from different leguminous crops from 16 agro-ecological regions of India was tested on mungbean (cv. Ratna), urdbean (cv. Barabanki local), cowpea (cv. V 578) and chickpea (cv. JG 62) under artificially inoculated conditions in pots. The isolates were highly variable in virulence and caused 10% to100% wet root rot incidence in mungbean, urdbean and cowpea and 11% to100% in chickpea. The isolates obtained from agro-ecological region 15 (western Himalayas, warm sub-humid ecoregion) caused significantly higher disease incidence in mungbean, whereas the isolates from agro-ecological region 10 (central highlands, hot sub-humid ecoregion) caused significantly higher disease incidence in urdbean and cowpea. In chickpea, the isolates from agro-ecological region 16 (Asom and Bengal plains, hot humid ecoregion) caused maximum disease incidence. The virulence of the isolates was also analyzed according to their crops of origin. Isolates from lentil caused the highest disease incidence in mungbean. Single isolate of rice bean caused the highest disease incidence in urdbean and cowpea, whereas kidney bean isolates caused the highest disease incidence in chickpea. The highest numbers of isolates covering maximum number of agro-ecological regions were obtained from mungbean followed by urdbean, cowpea and chickpea. One hundred thirteen isolates of the pathogen isolated from diseased roots were selected for aerial inoculation to test their ability to cause the aerial infection. All the isolates proved to be pathogenic to mungbean by aerial inoculation and caused 10%–50% disease incidence. The study clearly indicates that the pathogen is able to cause infection to the roots as well as aerial parts of the leguminous plant. The virulence of the isolates did not correspond to their region of origin, host, parts of plant and anastomosis groups.