Induced morphological and virulence variants of the obligate barley pathogen Erysiphe graminis f. sp. hordei

• Published in: Phytopathology Vol. 81; no. 11; pp. 1350 - 1357
• Main Authors: Sherwood, J.E, Slutsky, B, Somerville, S.C
• Format: Journal Article
• Language: English
• Published: St. Paul, MN American Phytopathological Society 1991
• Subjects: Agronomy. Soil science and plant productions; avirulence; Biological and medical sciences; conidia; Erysiphe graminis; Fundamental and applied biological sciences. Psychology; Fungal plant pathogens; gene interaction; gene-for-gene hypothesis; genotype; Hordeum vulgare; host-pathogen relationships; hyphae; mildews; mutagenesis; mutants; pathogenicity; Phytopathology. Animal pests. Plant and forest protection; plant morphology; powdery mildew; Variation, races, biotypes, parasitic specialization, genetics; virulence; Fungi; Scanning electron microscopy; Mutagenesis; Plant pathogen; Virulence; Ascomycetes; Erysiphe graminis f. hordei; Thallophyta
• ISSN: 0031-949X; 1943-7684
• DOI: 10.1094/Phyto-81-1350

A mutagenesis procedure designed to limit contamination was developed for Erysiphe graminis f. sp. hordei, an obligate pathogen that causes powdery mildew disease on barley. Gnotobiotic cultures of E. g. hordei were established on barley leaf sections placed on an agar medium in petri dishes. To mutagenize E. g. hordei, leaf sections with 3-day-old cultures were transferred to an agar medium containing ethyl methanesulfonate for 12-14 h. Seven days after mutagen treatment, the cultures were screened for morphological mutants. Among the classes of variants observed were those with red conidia and hyphae, round conidia, prematurely germinating conidia, and altered colony morphology. Based on the occurrence of red variants, the mutation frequency after exposure to ethyl methanesulfonate was estimated to be 1-2 X 10(-4). As a means of further analyzing host-pathogen interactions in the powdery mildew disease, mutants of E. g. hordei with increased virulence were generated with this mutagenesis protocol. A number of variants showing minor increases in virulence were recovered, but no fully virulent variants were observed. The mutation in one weakly virulent isolate was inherited as a simple, nuclear factor.