ABIOTIC STRESS AS A POTENTIAL CONTRIBUTING FACTOR TO ONSET AND SEVERITY OF INFECTION CAUSED BY LASIODIPLODIA THEOBROME AN OPPORTUNISTIC FUNGAL PATHOGEN IN COCONUT

Abstract

Coconut palms irrigated with water from bore wells in close proximity with oil exploration rigs reported sudden death later to the drilling of oil wells only since January 2021 and 2017 in Billakurru village and Lanka of Thane Lanka village, respectively from erstwhile East Godavari district of Andhra Pradesh. Isolations from infected samples yielded weak pathogens which usually affect plants subjected to stress. Pathogenicity tests with the isolated cultures of organisms were not successful on actively growing tissues but could produce symptoms on detached tissues indicating their status as weak pathogens. Adhoc attempts with fungicides to manage the likely pathogenic origin were unsuccessful. Abiotic stress is a potential contributing factor to onset and severity of disease caused by Lasiodiplodia theobrome that causes leaf blight disease in coconut. Under stress conditions invasion of opportunistic phytopathogen leading the infection at the base of the petiole and necrosis resulted drooping and yellowing of leaves. The progression of infection to growth point leading the toppling of rotten crown and emitting foul smell. Other crop plants like banana, turmeric, sweet orange, rice, sapota, mango etc. were found healthy without any signs of stress at all in the fields in which coconut was affected. Chemical analyses of soil, water and plant samples are attributed to higher salt concentration in general and Al in particular. Higher concentration of salts (EC) and Al in soil, water and plant samples in affected fields than in healthy fields were detected with decreasing values with increasing distance from the oil wells.