Impact of Soil Contents on Survival and Virulence of Ganoderma gibbosum Causing Basal Stem Rot in Coconut

Abstract

Basal stem rot caused by Ganoderma spp. is an important disease responsible for severe yield losses in coconut. As a soil-borne pathogen, Ganoderma can persist in soil for longer periods, and its survival and virulence are significantly affected by soil conditions. Soil moisture levels such as 20%, 40%, 60%, 80% of field capacity, field capacity level and flooded conditions were evaluated for their effects on survival and virulence of Ganoderma gibbosum. The pathogen was able to survive and cause disease at all soil moisture levels tested, with lower moisture levels being more favorable. Complete root infection or survival until six months was observed when soil moisture contents were 20%, 40% and 60% of field capacity. Among different soil types viz., sandy soil, sandy loam soil, silty soil and clayey soil evaluated, Ganoderma was able to survive and cause infections in sandy soils, silty soils and sandy loam soils better than clayey soils. Varied percentage of infection was observed for all soil types with a greater number of roots infected in the case of sandy soil (95.83%) followed by silty soil (91.6%), sandy loam soil (83.3%) and clayey soils (79.1%). Developing effective management strategies for Ganoderma requires an understanding of the effect of soil factors.