Effect of environmental factors on toxin production of Drechslera bicolor, a causal agent of leaf blight in bell pepper

Drechslera bicolor (Mitra.) Subram. and Jain, cause of leaf blight in bell pepper [Capsicum annuum var. grossum (L.) Sendt.], leads to necrotic lesions, early leaf senescence and yield losses. Detailed physiological analysis can contribute to an improved understanding of bell pepper disease interaction and cultivar improvement. D. bicolor produced maximum toxin in Richards’ medium and toxin was found most active at 25±2°C, pH 6.0 and 100% relative humidity. Different hosts were screened for disease resistance and it was observed that the partial purified toxin showed some degree of host specificity. Fungal toxin was able to produce symptoms in all the tested hosts with the main infected host being bell pepper. Prominent symptoms of chlorosis and wilting were observed on chilli followed by tomato, brinjal and lady finger. The detached leaf dip method followed by carborundum abrasion method was found to be the best inoculation methods in the production of wilting and chlorosis in bell pepper. These results indicated that the maintenance of physiological function during leaf blight infection could result in improved bell pepper yields under diseased conditions.