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Bacterial Reservoir of an Agent Infectious to Fungi. G. D. Lindberg, Professor of plant pathology, Department of Plant Pathology and Crop Physiology, Louisiana Agricultural Experiment Station, Louisiana State University, Baton Rouge 70803; Phytopathology 73:850-854. Accepted for publication 29 October 1982. Copyright 1983 The American Phytopathological Society. DOI: 10.1094/Phyto-73-850.

An irreversible disease condition was produced in Helminthosporium turcicum grown on potato-dextrose agar (PDA) or nutrient-dextrose agar (NDA) with established colonies of a pseudomonad bacterium; subcultures of the affected H. turcicum also were diseased. The disease developed without physical contact between the mycelium of H. turcicum and the pseudomonad colonies, which suggested an extracellular causal agent. Helminthosporium maydis race T and several other species of Helminthosporium grown with the pseudomonad on PDA or NDA changed markedly, but the change was not permanent; subcultures of the affected H. maydis race T were always normal. Mycelium of H. maydis grown with 1-wk-old colonies of the pseudomonad on peptone-dextrose-yeast extract agar (PDYA) with 1.2% peptone was normal and symptomless after 1 wk, then abruptly began to collapse and lyse; most subcultures of the treated H. maydis made 1 wk after commencement of lysis failed to grow, but surviving mycelium was normal. Symptom development was delayed ~1 wk when single conidia of H. maydis were placed on the PDYA with either 4-, 7-, or 10-day-old colonies of the pseudomonad. The causal agent was transmitted from diseased to healthy H. turcicum only after hyphal contact.