Pathogenicity on Ryegrass and Cultural Variability of Mississippi Isolates of Pyricularia grisea. L. E. Trevathan, Assistant Professor, Department of Plant Pathology and Weed Science, Mississippi State University, Mississippi State 39762. Plant Dis. 66:592-594. Accepted for publication 11 October 1981. Copyright 1982 American Phytopathological Society. DOI: 10.1094/PD-66-592.

The occurrence of Pyricularia grisea on hosts common to Mississippi was assessed to elucidate relationships among isolates and to determine their relative pathogenicity to Italian ryegrass (Lolium multiflorum). Isolates of P. grisea pathogenic to ryegrass were obtained from symptomatic leaf tissue of ryegrass, carbgrass (Digitaria sanguinalis), St. Augustinegrass (Stenotaphrum secundatum), spurge (Euphorbia preslii), and smartweed (Polygonum pensylvanicum) and from asymptomatic soybean (Glycine max) pod tissue. Colony morphology and growth rate varied with isolate and growth medium. The ryegrass cultivar Gulf was consistently more susceptible to the different isolates of P. grisea than was Magnolia.

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