Role of some Non-traditional Compounds in Managing Sugar Beet Powdery Mildew

Abstract

Certain non-traditional compounds such as compost tea, humic acid and sulphated canola oil were tested as foliar application to evaluate their efficacy to induce systemic resistance against Erysiphe betae, the causal agent of powdery mildew in sugar beet (Herkl cv.) versus the traditional fungicide Opera under greenhouse and field conditions at Gemmeiza Agricultural Research Station, Agricultural Research Center (A.R.C.), Egypt during two successive winter seasons (2014/2015 and 2015/2016). Under greenhouse conditions, results revealed that spraying plants with all the tested compounds reduced disease severity of powdery mildew. The fungicide Opera was the most effective treatment in reducing disease severity and increasing the efficacy followed by Sulplex, compost tea and humic acid. Also, all treatments significantly increased total phenols and orthodihydric (OD) phenol content of the leaves compared to the control 15, 30 and 45 days after inoculation. Also, spraying plants with the tested compounds increased the activity of peroxidase (PO), polyphenoloxidase (PPO) and chitinase enzymes compared to the control, 15, 30 and 45 days after artificial inoculation. Inthe detection of chitinase activity by using SDS-glycol chitin polyacrylamide gel electrophoresis the molecular weight for all samples ranged from 28 to 30 kDa. high intensity band expressing the highest chitinase activity was found in compost-tea treatment followed by Sulplex. Moreover, control, fungicide Opera and humic acid treatments showed low chitinase activity. Under field experiments, results indicated that the fungicide Opera was the most effective treatment for controlling powdery mildew followed by Sulplex and compost tea. Meanwhile, humic acid was the lowest effective one in this regard. All treatments increased root yield per feddan compared to the control. The fungicide Opera and Sulplex gave the highest root yield per feddan followed by compost tea then humic acid. Moreover, compost tea and Sulplex gave the highest percentages of total soluble solids (T.S.S.), sucrose percentages in beet roots and purity.