Role of non-conventional chemicals in biochemical defence against charcoal rot of sesame incited by Macrophomina phaseolina (Tassi) Goid

Abstract

Charcoal rot of sesame (Sesamum indicum) incited by Macrophomina phaseolina (Tassi) Goid. is an economically important disease in India and worldwide. Seed and soil borne nature, non-specific, wide host range of pathogen, difficult to manage with fungicides and absence of complete genetic resistance impelled to biochemical defence analysis against this pathogen. Treatment with non-conventional chemicals induces defence against pathogen in the form biochemical changes in plant. Hence, the present investigation was carried out to know the impact of non-conventional chemicals on changes in defence biochemical parameters in plant. As the concentration of different non conventional chemicals increased from 50, 100 and 200 ppm there was reduction in incidence of charcoal rot disease. Maximum induction of resistance was recorded by the application of salicylic acid at 200 ppm concentration after challenge inoculation with M. phaseolina followed by indole acetic acid, indole butyric acid, acetyl salicylic acid, riboflavin and thiamine. The activity of total phenols and sugar content was reached at peak after six days of challenge inoculation with the pathogen and subsequently activity of these parameters slightly declined after six days of inoculation in all tested non-conventional chemicals. At each concentration, SA showed maximum induction of total phenol and total sugar followed by IAA, IBA, ASA, thiamine and riboflavin. However, sesame variety HT 2 showed higher induction of biochemical activities and lower disease incidence of charcoal rot as compared to HT 1.