The Use of Antioxidants and Microelements for Controlling Damping-Off Caused by Rhizoctonia solani and Charcoal Rot Caused by Macrophomina phasoliana on Sunflower

Seed soaking method or foliar spray of antioxidants (citric acid and salicylic acid at 10 mM) and microelements (manganese and zinc at 2 g L-1) were tested to control of the damping-off and charcoal rot diseases of sunflower (varieties Sakha 53 and Giza 102). Field treatments in two different localities i.e., Tag El-Ezz, Dakahlia province and El-Serow, Damietta province were carried out. The high frequency isolated fungi (M. phaseolina and R. solani) presented in Tag El-Ezz location. On the other hand, M. phaseolina was isolated at a high frequency compared with R. solani in both locations. Sakha 53 was highly susceptible compered with Giza 102 when artificially infected with both M. phaseolina and R. solani. Laboratory results showed that salicylic acid alone or in combination with citric acid completely inhibited the linear growth of both pathogens i.e., M. phasoliana and R. solani in vitro. A positive correlation between the concentrations of Rizolex-T 50 and its effect on the fungal growth were recorded. The dose of 3 g L-1 prevented the growth of R. solani linear growth in vitro. The greenhouse results revealed that Giza 102 variety was highly susceptible to the infection by R. solani. M. phasoliana showed severe symptoms in both sunflower varieties. On contrary, Giza 102 variety was tolerant to damping-off and charcoal rot diseases than Sakha 53 under field conditions. The application of Rizolex-T 50 followed by citric acid showed a highest percentage of healthy plants followed by the combination of citric acid and salicylic acid. The application of manganese combined with zinc was more effective than the microelements alone. All treatments of antioxidants and microelements significantly reduced the incidence of charcoal rot disease. On the other hand, no significant differences between Rizolex-T 50 and salicylic acid treatments was shown. Sakha 53 variety gave the highest values of plant height and number of leaves plant-1 while Giza 102 recorded the highest values of stem diameter and flower head diameter. The application of citric acid combined with salicylic acid maximized the plant height followed by the mixture of manganese and zinc. Manganese treatment followed by the mixture of citric acid and salicylic acid then zinc were the most effective in increasing the number of leaves plant-1. While, Rizolex-T 50 had no significant effect on plant height and number of leaves plant-1. Microelements were more effective than antioxidants on enhancing the stem and flower head diameters. The combination between manganese and zinc followed by Rizolex-T 5