Biological control of cucumber powdery mildew (Podosphaera xanthii) (Castagne) under greenhouse conditions
Ehab Sarhan, Michael H. F. Abd-Elsyed, Azza M. Y. Ebrahiem
Abstract
Abstract Cucumber powdery mildew disease caused by Podosphaera xanthii (Castagne) U. Braun & Shishkoff severe disease-causing yield losses worldwide. This research study was conducted to evaluate the efficacy of the tested bio-agents, Trichoderma harzianum , T. viride , Bacillus subtilis , Paenibacillus polymyxa , and Serratia marcescens , as well as the fungicide score (Difenoconazole), on cucumber infected with P. xanthii , in vitro and under greenhouse conditions. Results indicated that culture filtrate of the tested bio-agents and the fungicide (control) significantly reduced P. xanthii conidial germination in vitro; the reduction percentage ranged between 91.17 and 76.06%. Also, score recorded the highest reduction percentage (97.19%). All treatments significantly decreased the disease severity and area under disease progress curve (AUDPC) post spraying the bio-agents on cucumber plants under greenhouse conditions. Score followed by B. subtilis significantly decreased disease severity percentage (67.33 and 65.38%, respectively) and AUDPC (322.84 and 342.06) than the untreated control (988.13 AUDPC). Additionally, treated cucumber plants showed a significant increase in plant growth parameters (plant height, total chlorophyll, fresh, and dry weight) and yield parameters (fruit number/plant and fruit weight/plant) as well the activity of defense-related enzymes, i.e., peroxidase (PO) and polyphenol oxidase (PPO), and total phenols content (TPC) compared to the untreated plants.