Bioactivity of methanolic plant extracts under in vitro conditions on inhibition of Stemphylium vesicarium an incitant of Stemphylium blight in onion

Abstract

Onion ( Allium cepa L.), an important vegetable and spice crop, is susceptible to Stemphylium blight incited by Stemphylium vesicarium . It causes significant losses (up to 80 %) in seed as well as bulb crops. The synthetic fungicides are the only option available to farmers for its management, which in long run may result in resistance development in pathogen. So there is a need to find novel strategies for management of this disease, hence the present study was devised to evaluate the antifungal efficacy of plant extracts from eight medicinally important plant species. The test fungus S. vesicarium was isolated from symptomatic leaf samples and was identified by characteristics of spore from available literature. Methanolic extracts of selected plants at three different concentrations (0.1, 0.5 and 1.0 %) were evaluated against S. vesicarium using poison food technique under in vitro conditions. The results showed that all plant extracts exhibited statistically significant antifungal efficacy from each other ( P < 0.05). But Origanum vulgare at 0.5 and 1 % concentration exhibited highest antifungal efficacy (68.23 % and 81.3 % respectively). The importance of the present study lies in that the oregano extracts had the potential to manage the disease under field conditions after isolation of bioactive molecule and development of proper formulation. To the best of our knowledge this is the first kind of study conducted, where oregano has been reported to be effective against plant pathogen.