Isolation and in vitro screening of potential biocontrol agents against powdery mildew of zucchini caused by Podosphaera xanthii

Abstract

Powdery mildew (PM) is an important disease of many plants worldwide. An in vitro screening protocol was developed for potential antagonists of PM isolated from naturally infected leaves of different plant species. A total of 2,000 isolates of bacteria, fungi and yeasts were tested in a preliminary screening process on detached leaves. Thirty isolates showing consistently good results were further tested under greenhouse conditions for their efficacy against PM of zucchini caused by Podosphaera xanthii (Castagne). Disease control of 30-77% was provided by 23 isolates in greenhouse trials, and significant reductions in area under disease progress curve (AUDPC) values were recorded as a result of 29 isolates being applied. Clonostachys rosea (Link) Schroers, Samuels, Seifert & Garns (syn. Gliocladium roseum), Trichothecium roseum (Pers.) Link (syn. Cephalothecium roseum) and three isolates of Serratia marcescens (Bizio) were the best five antagonists that were selected for further studies.