Biocontrol of Rhizoctonia solani Root Rot of Chilli by Bacillus subtilis formulations under Pot Conditions

Abstract

The chilli crop suffers massive yield loss due to root rot caused by Rhizoctonia solani. An increase of 10 í— 10⁵ root colonizing units/cm was obtained as a result of Bacillus subtilis in vitro root colonisation assay post germination. Shelf life studies of the formulations revealed stable population level of the biocontrol agent upto 180^th day (30°C - 1.6 í— 10⁸; 4°C - 1.9 í— 10⁸) in talc and upto 150^th day in lignite (30°C - 1.5 í— 10⁸; 4°C - 1.3 í— 10⁸). Soil, seed, foliar spray and dip treatment methods of B. subtilis and chlorothalonil brought about a considerable enhancement of all biometric parameters and reduced disease incidence compared to the untreated control. In comparison to the untreated control (50 g and 21 g fresh and dry weight, respectively), highest plant fresh weight (76.84 g) and dry weight (34.17 g) was achieved by the Seed application method. Comparison of plant height revealed maximum values 70 cm (soil application) and 77 cm (dip treatment) with B. subtilis application which was analogous to chlorothalonil treatment (56.5 cm with soil application and 70.33 cm with dip treatment) which was considerably superior to the untreated control (58.2 cm with dip treatment and 61 cm with soil application, respectively). Root dip treatment showed considerable increase in root length with B. subtilis (33 cm) and chlorothalonil (28.5 cm) when compared to untreated control (15 cm). Growth promotion was better with Root dip application while disease control was achieved better with seed application. A 66% and 84% reduction in incitation of disease was noticed with soil and seed application methods, respectively.