Atemperature-induced resistance to tan spot [pyrenophora tritici-repentis] of wheat

Abstract

Pyrenophora tritici-repentis (Ptr) induces tan necrosis and chlorosis in wheat. These symptoms are interaction phenotypes between individual isolates and specific wheat genotypes. The induction of tan necrosis is associated with the production of the Ptr-necrosis toxin by nec+ isolates of Ptr and the presence of a dominant gene for toxin sensitivity in the host. The effect of temperature on the development of tan necrosis and chlorosis was investigated using eight wheat genotypes differing in reaction to tan spot and three isolates from the three currently available virulent pathotypes of Ptr. The following constant temperature regimes were tested: 10, 15, 20, 22, 25, 27, and 30°C. At 27 and 30°C, a clear change towards resistance, both necrotic and chlorotic, was observed in the susceptible genotypes. Reaction types of the same lines/cultivars were not altered at temperatures of 25°C or below. Throughout this study, no breakdown of resistance was observed. Temperature-induced resistance to the fungus was paralleled by temperature-induced insensitivity to the Ptr-necrosis toxin. No symptoms were observed in toxin-infiltrated sensitive Glenlea wheat plants kept at 30°C. The data of this study suggest that, in the necrotic system, the induced resistance observed at temperatures above 27°C may have resulted from the failure of the toxin to interact with its putative receptor. © Taylor & Francis Group, LLC.