L. Lamari et al., IDENTIFICATION OF A NEW RACE IN PYRENOPHORA-TRITICI-REPENTIS - IMPLICATIONS FOR THE CURRENT PATHOTYPE CLASSIFICATION-SYSTEM, Canadian journal of plant pathology, 17(4), 1995, pp. 312-318
Pyrenophora tritici-repentis induces necrosis and chlorosis in its whe
at host. Isolates of the fungus have been grouped into four pathotypes
based on their ability to cause necrosis and chlorosis in differentia
l hexaploid wheat genotypes. Virulence tests on 39 isolates recovered
from samples collected in eastern Algeria indicated that these isolate
s had a virulence pattern different from those reported to date. All o
f the isolates from the Algerian collection were similar to those of p
athotype 3, as they caused chlorosis but not necrosis in differential
hexaploid wheats; however, the Algerian isolates induced chlorosis in
cv. Katepwa but not in line 6B365, which is used to differentiate isol
ates of pathotype 3 (virulent on 6B365) from those of pathotye 2 (avir
ulent on 6B365). A race designation is proposed to describe isolates o
f P. tritici-repentis on the basis of their virulence on differential
wheat lines, and not only on the necrosis-chlorosis symptoms they indu
ce in Glenlea and 6B365, a system which allows a theoretical limit of
only four pathotypes. Isolates originally ascribed to pathotypes 1, 2,
3, and 4 now represent races 1,2,3, and 4, respectively. The isolates
from eastern Algeria described in this study represent race 5. Isolat
es of race 5 produced the Ptr-necrosis toxin in culture. A wheat acces
sion (line 6B662), previously known to be resistant to isolates from a
ll pathotypes, developed chlorosis to race 5, suggesting the potential
of this pathogen to overcome resistance of its host.