Effect of Foliar Application of some Zinc and Phosphorus Sources on Controlling Helminthosporium Leaf Spot Disease and Production of Sesame

Abstract

Nineteen isolates of Helminthosporium sesami were obtained from infected sesame plants with Helminthosporium leaf spot taken from different locations in Nubaria region, El-Behera Governorate, Egypt. All the obtained isolates of the pathogen were able to infect Del Al-Jamal sesame variety plants causing Helminthosporium leaf spot disease symptoms with different degrees. The objectives of this study were to evaluate the efficiency of some zinc and phosphorus sources against the pathogen and their effect on some agronomic characters of sesame. In vitro studies, the effects of zinc oxide (ZnO), zinc sulfate (ZnSO 4) as sources of zinc and dipotassium phosphate (K 2 HPO 4) and disodium phosphate (Na 2 HPO 4) as sources of phosphorus on the pathogen have been studied by using different concentrations on potato dextrose agar medium (PDA). These results suggest that these compounds reduced the mycelial growth of the pathogen. The highest reduction of mycelial growth was obtained when ZnSO 4 at concentration 100 mM (78.57%), followed by ZnO. Under field experiments, foliar spraying of sesame plants with ZnO, ZnSO 4 , K 2 HPO 4 and Na 2 HPO 4 at the rate of 100 mM reduced disease severity compared to the control treatment. ZnO gave the highest reduction in disease severity followed by ZnSO 4. These compounds improved agronomic characters of sesame, i.e. plant height, number of branches and capsules/plant, weight of 1000 seeds (g), seed yield/feddan and percentage of oil seeds. K 2 HPO 4 treatment was the most effective on all studied agronomic characters than other compounds.