Predominance in New York of Isolates of Exserohilum turcicum Virulent on Maize with Gene Ht1. N. P. Keller, Department of Plant Pathology, Cornell University, Ithaca, NY 14853-5908. G. C. Bergstrom, Department of Plant Pathology, Cornell University, Ithaca, NY 14853-5908. Plant Dis. 74:530. Accepted for publication 23 March 1990. Copyright 1990 The American Phytopathological Society. DOI: 10.1094/PD-74-0530A.
>Exserohilum turcicum (Pass.) Leonard & Suggs, causal fungus of
northern maize leaf blight, has been characterized by several physiologic
races and two mating Iypes (1,2). Twenty-eight isolates of E.
turcicum were collected from blighted maize (Zea mays L.) leaves
in New York (representing 12 counties, predominantly in the southern
tier of counties) during 1985-1987. All 28 isolates were virulent on
differential maize inbreds Oh43 and Oh43 Ht1 and avirulent on Oh43
Ht2, a virulence pattern recently designated as race 1 (1). This is
consistent with the widespread deployment in New York of hybrids
containing gene Htl. The mating type of the isolates was determined
by making sexual crosses with lester isolates of known mating type.
Of seven isolates that produced fertile crosses (i.e., formation of mature
perithecia containing ascospores), one was identified as mating type
A and six as mating type a. The presence of both mating types within
the New York population of E. turcicum suggests an increased potential
for sexual recombination and evolution of new variants of the pathogen
in this region.