Wheat Genotypes that Develop Both Tan Necrosis and Extensive Chlorosis in Response to Isolates of Pyrenophora tritici-repentis. L. Lamari, Assistant Professor, Department of Plant Science, The University of Manitoba, Winnipeg, Manitoba, Canada R3T 2N2. C. C. Bernier, and R. B. Smith. Professor, and Technical Assistant, Department of Plant Science, The University of Manitoba, Winnipeg, Manitoba, Canada R3T 2N2. Plant Dis. 75:121-122. Accepted for publication 6 July 1990. Copyright 1991 The American Phytopathological Society. DOI: 10.1094/PD-75-0121.

Wheat cultivars commonly develop either tan necrosis (nec) or chlorosis (chl) in response to infection by Pyrenophora tritici-repentis. We report, for the first time, wheat genotypes capable of developing both symptoms. Isolates of P. tritici-repentis can be classified on the basis of their ability to induce tan necrosis and/or extensive chlorosis. A selection of winter wheat cultivar Norstar and spring wheat line 6B699, tested to isolates from pathotypes 1 (nec+ chl+), 2 (nec+ chl–), 3 (nec– chl+), and 4 (nec– chl–), developed tan necrosis in response to nec+ isolates as well as extensive chlorosis in response to chl+ isolates. Both lines were sensitive to the Ptr-necrosis toxin. This finding suggests that tan necrosis and extensive chlorosis are controlled by different genes.