L. Lamari et Cc. Bernier, TEMPERATURE-INDUCED RESISTANCE TO TAN SPOT [PYRENOPHORA-TRITICI-REPENTIS] OF WHEAT, Canadian journal of plant pathology, 16(4), 1994, pp. 279-286
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+ is
olates of Ptr and the presence of a dominant gene for toxin sensitivit
y in the host. The effect of temperature on the development of tan nec
rosis and chlorosis was investigated using eight wheat genotypes diffe
ring in reaction to tan spot and three isolates from the three current
ly available virulent pathotypes of Ptr. The following constant temper
ature regimes were tested: 10, 15, 20, 22, 25, 27, and 30 degrees C. A
t 27 and 30 degrees C, a clear change towards resistance, both necroti
c and chlorotic, was observed in the susceptible genotypes. Reaction t
ypes of the same lines/cultivars were not altered at temperatures of 2
5 degrees C or below. Throughout this study, no breakdown of resistanc
e was observed. Temperature-induced resistance to the fungus was paral
leled by temperature-induced insensitivity to the Ptr-necrosis toxin.
No symptoms were observed in toxin-infiltrated sensitive Glenlea wheat
plants kept at 30 degrees C. The data of this study suggest that, in
the necrotic system, the induced resistance observed at temperatures a
bove 27 degrees C may have resulted from the failure of the toxin to i
nteract with its putative receptor.