Vol. 12, Issue 7 (2023)

Author(s):
P Jeevitha, Dr. P Mahalakshmi, Dr. I Yesu Raja, Dr. K Sujatha, Dr. ML Mini and M Ayyandurai

Abstract:
This study aimed to investigate the occurrence and severity of twister blight disease in onion crops in selected villages of Tamil Nadu, India. The disease incidence ranged from 33.45% to 86.96% across the surveyed villages, with the highest incidence recorded in Kalvelipatti village of Madurai district (86.96%), followed by Kesampatti village in Madurai district (79.89%), and the lowest incidence in Pottikampatti village of Dindigul district (33.45%). The isolated pathogen exhibited characteristics such as non-septate mycelium, bullet or cylindrical-shaped spores, and the formation of pale orange-colored acervuli above the mycelial growth. Pathogenicity tests were conducted on ten different isolates of Colletotrichum gloeosporioides, with OCMK-3 demonstrating the highest virulence (97.75% disease incidence) followed by OCDP-2 (90.77%). Furthermore, seaweed extracts were prepared from collected seaweeds using different solvents (methanol, ethyl acetate and hexane) and evaluated for their antifungal activity against the pathogen. The agar well method was employed for in vitro screening, and Sargassum cristaefolium exhibited the highest inhibition of mycelial growth (73.00%) under aseptic conditions. This study provides valuable insights into the prevalence of twister blight disease in onion crops and highlights the potential of seaweed extracts as a natural antifungal agent.