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Processes of Sporulation in Alternaria solani and their Response to Metabolic Inhibitors. R. J. Lukens, Plant Pathologist, Department of Plant Pathology and Botany, The Connecticut Agricultural Experiment Station, New Haven 06504 ; J. G. Horsfall, Senior Scientist, Department of Plant Pathology and Botany, The Connecticut Agricultural Experiment Station, New Haven 06504. Phytopathology 63:176-182. Accepted for publication 3 July 1972. DOI: 10.1094/Phyto-63-176.

Hyphae and conidiophores of Alternaria solani are both filaments. In that sense, both conidiophores and spores arise as buds from filaments. Both budding processes require oxygen and are inhibited by carbon dioxide. They are highly sensitive to azide, dinitrophenol, and thiol reagents, but not to cyanide nor fluoride. Acridine and 2 phenylcarbamates as well as several phenoxyacetic acids and other inhibitors of glycolate oxidase were toxic to both budding processes. These results suggest that respiration of budding involves an iron-flavin terminal system that has a high affinity for oxygen. Budding may require ATP and thiols. The oxidation of glycolic acid and the subsequent utilization of glyoxylic acid appear essential to budding. Budding seems to involve synthesis of nucleic acids and proteins. Oligomycin, 8-azaguanine, and 2-thio-6-oxypurine inhibit formation of conidiophores but not spores. Apparently, these differences in budding response between a hypha and a conidiophore reflect slight differences between the two filaments. Budding, therefore, can be a target at which to direct a search for new fungicides of high selectivity.