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Ecology and Epidemiology

Comparative Nutrient Dependency of Botrytis squamosa and B. cinerea for Germination of Conidia and Pathogenicity on Onion Leaves. C. A. Clark, Graduate Research Assistant, Department of Plant Pathology, New York State College of Agriculture and Life Sciences, Cornell University, Ithaca, NY 14853; J. W. Lorbeer, Professor, Department of Plant Pathology, New York State College of Agriculture and Life Sciences, Cornell University, Ithaca, NY 14853. Phytopathology 67:212-218. Accepted for publication 15 June 1976. Copyright © 1977 The American Phytopathological Society, 3340 Pilot Knob Road, St. Paul, MN 55121. All rights reserved.. DOI: 10.1094/Phyto-67-212.

Germination of conidia and germ tube length of isolates of Botrytis squamosa were similar in water and nutrient solution. Spraying conidia in water onto leaves resulted in production of expanding lesions. The frequency of lesions was increased by addition of nutrients to the inoculum. Germination of conidia of all isolates of B. cinerea was significantly lower in water than in nutrient solution. Germ tube elongation in water ceased almost immediately upon emergence of the germ tube from the conidium. Spraying onion leaves with conidia suspended in water failed to produce lesions, but addition of an exogenous nutrient source resulted in formation of expanding lesions. Nutrient dependency of conidia of B. cinerea, but not of B. squamosa, increased with increased age of dry-harvested conidia. Combining the two species during incubation had no effect on conidial germination. Leaching conidia of either species with water inhibited germination, but leaching with nutrient solution did not. Conidial germination and lesion formation (numbers) by both species were increased by diffusate from the onion-leaf lacuna, filtrate from cattail pollen, or by Czapek-Dox broth amended with yeast extract. Glucose (1%) was a weak stimulant for both germ tube elongation and lesion formation.