الفهرس | Only 14 pages are availabe for public view |
Abstract Abstract Damping-off and root rot is a serious disease infecting cucumber on both seedling and adult stages under protected cultivation causes severe losses in the cucumber yield. A survey was conducted in five countries at fayoum governorate during the growing seasons 2017/ 2018. Over all averages of disease incidence and disease severity were 30.06 and 57.37% respectively. 237 fungal isolates were isolated from cucumber plants and identified. The pathogenicity test of 19 isolates were chosen to represent all the surveyed districts of Fayoum governorate. Pathogenicity tests revealed that four isolates (R. solani, M. phaseolina, F. oxysporium and F. solani) caused the highest damping-off and root rot disease incidence of cucumber. Five cucumber cultivars have been used to determine is susceptibility to infected by the tested fungi. The tested fungi were retested on eight plant species belong to four plant families: Cucurbitaceae, Fabaceae, Brassicaceae, and Apiaceae to determine host range. In vitro inhibitory of six trichoderma isolates, five antagonistic bacterial isolates, two Streptomyces isolates, three humic substance and six resistance inducers were evaluated against the tested pathogenic fungi. The highest average percentage of growth reduction recorded by T. asperillium TA1 (86.85%), B. subtilis B1 (75.46%), P. fluorescens PF1 (72.87%) and Streptomyces spp St1 (64.44%). The inhibitory effect of humic substances and resistance inducers significantly reduced the average mycelium growth of tested fungi. The highest growth reduction of tested fungi was for humic substances at concentration 200 µL, chitosan and H 2 O 2 at 150 mg and 20 mM concentration respectively, Salts and antioxidant at concentration 15 mM, by salicylic, citric and ascorbic acid While, potassium iodide at concentration 5 mM. Under greenhouse integrated efficacy of the best treatments from laboratory experiments were studied against cucumber root rot disease as individual treatments and mixed treatments for the best results with individual treatments. All the selected treatments individually or in combination reduced the percentage of cucumber damping off and root rot incidence compared to the control in both fayoum and giza experiments. Most all the tested treatments led to an increase in growth parameters such as plant height, wet, dry weight, yield and the total chlorophyll. Also, gave the best results for increasing in oxidative enzymes activity and total phenol in roots of cucumber plants compared to the control. The best treatments improve in the roots anatomic structure of the treated cucumber plants compared to the untreated plants. Key words: Cucumber, Damping off, root rot, F. oxysporium, F. solani, M. Phaseolina, R. solani, Bioagents, Humic substances, resistance inducers, enzymatic activity. |