الفهرس 
Survey of cucumber damping off and root rot diseaseOnly 14 pages are availabe for public view
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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.