الفهرس 
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Abstract
Potato (Solanum tuberosum L.) established as the fourth main food crops worldwide. Surveillance presents 40 soil-borne pathogens significantly affect potato growth causing outbreak in diseases incidence. However, researchers show that nearly 40 soil-borne pathogens may affect potatoes during their life span leading to a rapid loss in the yield Potato tubers collected from different locations at Dakahlia governorate (Kotama - Batra - Altawila) were found infected with Fusarium solani (2 isolates), Fusarium oxysporum (3 isolates) and Rhizoctonia solani (2 isolates).The degrees of variation in pre, post-damping-off and stunted seedlings caused by F. oxysporum, F. solani and R. solani isolates show that F. oxysporum (isolate 3), F. solani (isolate 1) and R. solani (isolate 2) were the most aggressive isolates affect potato tubers.Salicylic acid at the concentrations of (0.5, 1, 1.5, 2 g/L), tartaric acid at (2, 2.5, 3, 3.5 g/L), citric acid at (2, 2.5, 3, 3.5 g/L) and GAWDA® formulation at (2, 2.5, 3, 3.5 g/L) significantly decreased the in vitro growth of F. oxysporum, F. solani and R. solani isolated from potato tubers. The application showed that GAWDA® formulation at the concentration (3.5 g/L) significantly increased the Plant length, root length, shoot length, plant weight, root weight, shoot weight and weight of tubers/plant of potato plants under stress of F. oxysporum, F. solani and R. solani infection.In field trails, soaking tubers in 3.5 g/L of GAWDA formulation for half an hour before planting followed by three successive sprayings with the same concentration started on reaching 30 days old and with 15 days interval spray showed a positive effect on decreasing the pre, post-emergence damping-off and stunted seedlings as well as scale up the percentage of normal seedlings in compare to the check treatment.The effect of the selected antioxidants on photosynthetic pigments and total phenol content in potato plants showed that GAWDA® formulation at a concentration 3.5 g/L significantly increased the content of photosynthetic pigments and total phenol in the leaves of 30, 45, 60 and 75 days old plants.The effect of the selected antioxidants on growth parameters and yield components i.e. Plant length, root length, shoot length, plant weight, root weight, shoot weight, weight of tubers/plant and weight of tubers/feddan of potato plants were studied. The application showed that GAWDA® formulation at the concentration (3.5 g/L) significantly increased the Plant length, root length, shoot length, plant weight, root weight, shoot weight, weight of tubers/plant and weight of tubers/feddan of potato plants.The possible role of the selected antioxidants on the total content of sugar in potato tubers was carried out in form of seed soaking, spraying started on 30 days old plants and soaking followed by three interval times of spraying plant leaves on 30, 45, 60 and 75 days old plants.It was also found that GAWDA® formulation significantly decreased the content of total sugar in the fresh tubers followed by Tartaric acid at the same concentration came after, while Salicylic acid was the least effective treatment on the total sugar content in the tubers.The effect of the selected antioxidants on the starch, potassium and carotene content in potato tubers was studied . GAWDA® formulation at a concentration of 3.5 g/L and in form of soaking plus spraying significantly increased starch content in tubers to record 12.27% , potassium content in tubers to record 3.98 % and carotene content in the fresh tubers to record 2.07 mg/100g .The results presented here recommend potato growers to apply the green chemicals in form of antioxidants to produce quality tubers and higher yield. The recommended technique is to soak the tuber cuttings before sowing in water solution of the formulated antioxidant GAWDA® of 3.5 g/L for 30 min followed by 3 interval sprays from the same concentration of the GAWDA® formulation on 30,45,60 and 75 days old plants . This for sure, will accelerate the growth and produce quality tubers and increase the yield by 33 % . Also protect the environment from the hazards pesticides.