Systemic Resistance in Snap Bean (Phaseolus vulgaris L.) Elicited by Some Chemicals and Biotic Inducers Against White Mold Disease Caused by Sclerotinia sclerotiorum

Abstract

he effect of chemicals and biotic inducers i.e., Bion [benzothiadiazole (BTH)], Salicylic acid (SA), Bacillus subtilis and Trichoderma harzianum as seed treatments of snap bean (Phaseolus vulgaris L. cv. Paulista.) compared to the fungicide Topsin M-70, were evaluated in the greenhouse and under field conditions during the two successive growing seasons 2016/2017 and 2017/2018 at Ashmoun, Menoufia Governorate, Egypt to control the white mold disease caused by Sclerotinia sclerotiorum (Lib.) de Bary. All the tested chemicals and biotic inducers treatments significantly reduced the percentages of pre-and post-emergence damping-off compared with the untreated control under greenhouse conditions. The highest percentage of survived plants was achieved by Topsin M-70 and Bion, followed by B. subtilis, Salicylic acid, and T. harzianum. Activities of defense-related enzymes peroxidase (PO), polyphenoloxidase (PPO) enzymes, and phenol content were determined. Bion treatment showed the highest increase in PO and PPO activity and total phenols followed by B. subtilis, Salicylic acid, and T. harzianum treatments in the presence of S. sclerotiorum. In the two successive growing seasons under field conditions, all the tested chemicals and biotic inducers treatments reduced the percentage of white mold incidence and severity of the treated snap bean plants compared with the untreated control. The highest reduction of disease incidence and severity was recorded by Topsin M-70 followed by Bion, B. subtilis, Salicylic acid, and T. harzianum, respectively. As well as, all treatments significantly increased vegetative characteristics i.e., plant height, No. of branches/plant, plant fresh and dry weight, and yield parameters i.e., average pod weight (g) and yield (ton/fed). Furthermore, chemical composition of green pods showed a significant increase in protein and carbohydrates content (%) beside all minerals Nitrogen (N), Phosphorus (P) and Potassium (K) content as compared with the untreated control in the two growing seasons.