Induced Resistance against Bipolaris bicolor, Bipolaris sorokiniana and Drechslera tritici‐repentis in Wheat Leaves by Xantham Gum and Heat‐Inactivated Conidial Suspension

Foliar‐applied xantham gum, commercially available exopolysaccharides from Xanthomonas campestris pv. campestris bacterial capsule, together with conidial suspension of heat‐inactivated pathogens were tested in relation to their ability to induce local and systemic protection against leaf spot diseases caused by Bipolaris sorokiniana, Bipolaris bicolor and Drechslera tritici‐repentis. Xantham gum preparation and heat‐inactivated conidial suspension were effective in inducing local and systemic protection when applied 48 h before the challenge with the pathogen. Microscopic studies of pathogen development in protected and control leaves indicated that neither germination and appressoria formation nor number of papillae were affected by treatment with xantham gum and heat‐inactivated conidial suspension. Increased activity of β‐1,3 glucanases was correlated with the induction of resistance and showed that protection induced in wheat leaves treated with the fungicide propiconazole presented a different mechanism of action.