Leaf assay screening antagonistic microorganisms to control Rhizoctonia solani causing leaf web blight of durian.

摘要

Rhizoctonia solani caused severe rot and blight to a wide range of plants. Damage occurred from seedlings to mature plants. Leaf web blight is one of the most serious diseases of durian growing in the heavy rainy southern part of Thailand. Screening antagonistic microorganism to use as biological control agent is a sustainable acceptation approach to control the disease recently. Leaf assay was used to screen and confirm antagonist. The healthy plant, web blight leaf and soil at rhizosphere were sampled from the orchard at Nakon Si Thammarat and Krabi. Leaf wash technique and soil surface dilution were isolation methods to collect antagonistic microorganisms from the leaf and soil samples from the farmer orchard. Dual culture was used to preliminary screen. Nine of 38 isolates were effective antagonistic bacteria and six of 15 isolates were effective antagonistic fungi. Leaf assay was done to confirm antagonistic efficacy. The 3 most effective antagonistic fungi and 3 most effective antagonistic bacteria were selected to confirm by leaf assay. Only KBNL3 fungal isolate curtained control on leaf assay. It protected against infection of R. solani on leaf better than copper oxychloride after 7 days inoculation. It still controlled completely after 15 days inoculation while leaf sprayed with copper oxychloride was completely infected.