Enhanced onion resistance against Stemphylium leaf blight disease, caused by Stemphylium vesicarium, by Di-potassium phosphate and benzothiadiazole treatments

Abstract

In this study, we investigated the induced defense response and protective effects against Stemphylium vesicarium by application of benzothiadiazole (Bion®) and di-potassium phosphate salt (K2HPO4) to onion. Onion leaves were sprayed with Bion® and K2HPO4, then inoculated 2 days later with a virulent strain of S. vesicarium under greenhouse conditions. Disease severity and activities of peroxidase (PO), polyphenoloxidase, phenylalanine ammonia-Iyase (PAL) and phenol contents were evaluated in the treated leaf tissues. Reduction in the disease severity was observed in plants treated with Bion® and K2HPO4. Onion plants treated with Bion® and K2HPO4 and inoculated with the pathogen showed significantly higher PAL activity, PO activity, and phenol contents than inoculated water-treated plants 2 days after the treatment. In conclusion, the results of this study provide evidence that application of simple non-toxic chemical solutions as di-potassium phosphate and Bion® can control Stemphylium leaf blight of onion. © The Korean Society of Plant Pathology.