الفهرس 
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Abstract
The present study aimed to use antioxidants as safe, environmentally-friendly and effective means to manage F. verticillioides and H. maydis the causal agents of stalk rot and late wilt diseases, respectively in maize plants. Also, to evaluate the ability of antioxidants to improve maize growth and productivity. 1- Thirty samples of maize seed were collected from growing fields of Dakahlia, Kafr El-Shaikh and Cairo governorates, Egypt seed health test was carried out following the procedures published by the International Seed Testing Association (ISTA) using AP and SB techniques. 2- A total of eighteen genera comprise thirty-five species of fungi were recovered from the collected samples. 3- The obtained data showed that F. verticillioides (100%), P. spp. (96.7%), A. flavus (76.7%) and A. niger (83.3%) were most common. 4- Among the recovered fungi, F. verticillioides was detected as the most common pathogenic ones. The F. proliferatum (50%), C. acremonium (43.3%) and Nigrosporaoryzae (40.0%) were recorded at moderate percentages. 5- The natural transmission study of the isolated fungi and elucidation of the mode of their transmission from seed to seedlings was undertaken. six kernel rot pathogens i.e., A. alternata, A. flavus, A. niger, F. verticillioides, Penicillium spp. and H. maydis proved their abilities to transmit to the germinating seeds and cause pre-emergence and post-emergence death. 6- F. verticillioides seed-infection recorded the highest percentage of seed-borne infection (70%), pre-emergence death or seed rot (16%), seedling infection (7%), post-emergence death (12%) and total disease development (35%). 7- Four seed-borne fungi with historical pathogenic effect namely; Aniger, H. maydis, F.verticillioidesandF. proliferatumwere used to study their pathogenicity on maize seed and seedlings. Among the tested fungi, F. verticillioides and F. proliferatum showed the highest seed rot and seedlings mortality symptoms (20.3& 15 and 17.5 & 13.5%, respectively), followed by H. maydis (15.5 & 8.5%, respectively) as compared to the check (4.0 & 1.0%, respectively). 8- Four selected antioxidantsi. e., salicylic acid (SA), benzoic acid (BA), hydroquinone (HQ) and tartaric acid (TA) as well as the formulated antioxidant GAWDA® (Patent No. 23798) were tested for reducing the linear growth of F. verticillioides and H. maydis pathogens. Six concentrations (0, 1, 3, 5, 7 and 9 mM) of each antioxidant were selected. The chemical fungicide Vitavax® 200 FS 40% at the rate of 3.5 cm3 /1000 mL was used as positive control. 9- Results revealed the highest reduction in linear growth of F. verticillioides pathogen in the treatments of BA, GAWDA® formulation and HQ even at lower concentrations (1 mM). In this connection, the degree of inhibition was directly proportional to the antioxidant concentrations. The same strong effect was attained on the growth of H, maydis pathogen when 3 mM of GAWDA® formulation, 5 mM of BA and 7 mM of HQ were used. 10- In pot experiments, data indicated that soaking maize seeds in antioxidants substances for 3hr before sowing significantly decreased the percentage of disease incidence of maize under the artificial infection by either of F. verticillioides (FV) or H. maydis (HM) pathogens in comparison with the untreated infected control. 11-Vitavax® (3.5 cm3 /1000 mL), BA (9mM), HQ and GAWDA® formulation (9mM) had the highest effect on reducing the percentage of disease incidence at the seedling stage. Similar disease reduction in seedlings mortality due to infecting with H. mydis pathogen, and consequently the highest increasing of the percentage of survived plants up to 83.33 and 95.29%, respectively were recorded by both HQ and GAWDA® formulation as compared to infected control (64.29%). 12- The obtained data showed that treated seeds by selected antioxidants and GAWDA® formulation enhanced growth parameters of maize plants over the control either infected or uninfected plant with F. verticillioides and H. maydis pathogens. In this respect, HQ, GAWDA and the recommended fungicide showed similar increasing of plant height parameter (171.5, 170.33 and 187.50 cm, respectively) as compared to untreated-infected control (144.00 cm). Also, HQ, BA and Vitavax had the highest effects in increasing plant fresh and dry weights (114.17, 113.17, 121.33g and 43.33, 41.93, 42.57g, respectively) as compared to infected control (93.33 and 29.79, respectively) under infection with F. verticillioides. Such a significant increase in plant height, fresh and dry weights characters, however, were greatly marked when BA, SA, HQ, GAWDA and Vitavax® applied as compared to infected control with H. maydis. 13- A significant physiological response of maize plants in terms of total phenols, polyphenoloxidase (PPO), peroxidase (POD) and photosynthetic pigments contents due to all investigated antioxidants and GAWDA® formulation treatments. 14- Under infection stress with F. verticillioides, seed treatment by HQ(35.52 mg catechol 100g-1 FW), followed by BA and GAWDA® formulation (30.74 and 32.20 mg catechol 100g-1 FW) treatments recorded the highest significant increase in total phenol contents as compared to Vitavax® and untreated-infected control (14.95 and 26.70 mg catechol 100g-1 FW, respectively). In respect to PPO activity, treatments of BA and HQ came in the second order (24.67 and 25.33 Unit-1 min g-1 fresh wt., respectively) as compared to infected control (16.00 Unit-1 min g-1 fresh wt.). POD increased also by Vitavax® or BA application (6.22 and 6.40 Unit-1 min g-1 fresh wt., respectively), as compared to infected control (1.78 Unit-1 min g-1 fresh wt.). 15- In the presence of H. maydis pathogen, such significant increase in plant total phenol contents (28.45 mg catechol 100g-1 FW) was recorded by GAWDA® treatment, followed by HQ and Vitavax® (22.29 and 19.72 mg catechol 100g-1 FW) as compared to infected control (17.69 mg catechol 100g-1 FW). A similar increase in PPO activity (58.67 and 35.33 Unit-1 min g-1 fresh wt., respectively) was recorded by GAWDA and Vitavax® as compared to infected control (27.33 Unit-1 min g-1 fresh wt.). 16- Concerning photosynthetic pigments, SA and Vitavax®treatments showed the highest significant increase of Chl a and total Chls pigments (0.61, 0.47 and 0.77, 0.60 mg g-1 FW.) as compared to infected F. verticillioides control (0.30 and 0.40 mg g-1 FW., respectively).Such significant increase was recorded in the presence of H. maydis pathogen, in Chl a, total Chls and carotenoids contents due to SA, HQ and GAWDA applications as compared to infected control. 17- Under field conditions, generally, seed treated with different antioxidants and GAWDA formulation followed by BA showed a significant decrease in diseases incidence and increase of most all plant growth characters (plant height, number of leaves and Fresh weight plant-1) compared to Vitavax® and control treatments. Such significant increases were recorded in most maize yield component (corncob weight, corncob length, no. of corncob rows and no. of grain raw-1), due to seed treated with different antioxidants and GAWDA formulation applications.