الفهرس 
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Abstract
Along the last 10 yeares, grape growers at EL-Minia governoreate, Egypt were suffered from growth and yield weakness of grape plants. They had to remove viticultures and planted alternative crops. Thus, the present work was concerned to through light on grapevine root rot and wilt diseases.
The obtained results could be summarized as follows:
Pathological studies:
Grapevine root rot prevalence, incidence and severity were varied with plant age and grape variety. Young vineyards (1-3 years old) provided the highest values of prevalence, incidence and severity at Minia governorate, Egypt.
Roomy grapevine variety recorded prevalence; incidence and severity values for root rot higher than Superior grapevine variety.
Isolates of Fusarium sp. were the most frequent fungi associated with rotted grape roots followed by Rhizoctonia solani isolates, while other fungi viz. Alternaria sp. Aspergillus sp. Penicillium sp. Diplodia sp. and Nigrospora sp. were the least frequent.
Among 10 fungal isolates tested, Fusarium sp isolate G5 was the most infective followed by R. solani isolate G3 and Fusarium sp isolate G1.
Identification of the most pathogenic isolates was confirmed as F. solani isolates G1 and G5 and R.solani isolate G3 that were used further.
Varietal response to root rotting fungi was varied with grapevine varieties and fungal isolates. Black desert grapevine variety exhibited resistance against F. solani and R. solani infection. Two grapevine varieties, Flame seedless and Early sweet reacted as moderately infected. The most susceptible variety was Superior followed by Roomy.
Three plant species i.e., clover, cumin and tomato plantes were infected by R. solani and F. solani isolates tested, but barley,broad bean and wheat plantes were not infected.
Laboratory studies:
Both linear growth (LG) and mycelial dry weight (MDW) for all fungal isolates tested were significantly affected by temperature degrees. The highest LG and MDW were provided at 25OC.
Out of 6 growth media tested, Czapeck’s medium showed the highest LG and MDW of all fungal isolates tested followed by PDA medium.
Growth perameters viz LG and MDW were significant reduced by acetic acid and or/H2O2 A synergesctic effects were exhibited by mixing AA+ H2O2. Since the highest reduction in LG or MDW was pronounced at 0.2 g/l AA+ 2.0 g/l H2O2 .
Antifungal effects were significantly explored by adding citric acid and or/ H2O2 to the growth medium for F. solani isolates G1 and G5 or R. solani isolate G3. Combining CA + H2O2 exhibited the highest reduction in both LG and MDW.
Potassium bicarbonate (Pb) showed the most antifungal compound against F. solani and R. solani isolates tested as compeared to AA, CA and even H2O2 alone .Mixing Pb with H2O2 gave the highest antifungal effects.
Potassium silicate (Ps) showed antifungal activity towards F. solani isolates G1 and G5 and R. solani isolate G3. Increasing Ps concenterations significantely increased LG and MDW. A beneficial effect for potassium silicate against fungal growth was pronounced at 2mM.
Possible mangmentes:
Both RRI and RRS were significantly reduced upon AA and or/ H2O2 treatments. The highest protection occured by 0.2 g/l AA+ 2.0 g/l H2O2.
Application of CA and/ or H2O2 to grapevine cuttinges (Superiour var.) resulted in significante RRI and RRS reduction. Combining 0.2 g/l CA+ 2.0 g/l H2O2 achieved the highest protection as compeared to individual application of 0.2 g/l CA or 2.0 g/l H2O2.
An obvious RRI and RRS reduction were provided by Pb and/or H2O2 . A significant protection was obtained by individual Pb or H2O2 application and a synergesctic effect was explored by mixing both Pb and H2O2 . The highest protection values was given by 0.2 g/l Pb + 2.0 g/l H2O2 combination.
A beneficial effect for potassium silicate against grapevine root rot caused by F. solani isolates G1 and G5 or R. solani isolate G3 was expressed 2 mM.