VIEW ARTICLE

Ecology and Epidemiology

Growth of Cereal Root-Rot Fungi as Affected by Temperature-Water Potential Interactions. R. James Cook, Research Plant Pathologist, Agricultural Research Service (ARS), U.S. Department of Agriculture (USDA), Washington State University, Pullman 99163; Alice A. Christen, Research Assistant, Department of Plant Pathology, Washington State University, Pullman 99163. Phytopathology 66:193-197. Accepted for publication 11 August 1975. DOI: 10.1094/Phyto-66-193.

Fusarium roseum ‘Graminearum’, F. roseum ‘Culmorum’, and Gaeumannomyces graminis var. tritici all required progressively drier conditions on osmotically-adjusted agar media for maximal growth, when the temperature of incubation was raised from 10 C to 35 C. An isolate of Graminearum from corn, and one from wheat, both grew optimally at –10 to –28 bars at 20 to 30 C and at –28 to –55 bars at 35 C. Three isolates of Culmorum from different areas each grew optimally at –8 to –14 bars at 20 to 30 C and at –28 bars at 35 C. Gaeumannomyces graminis grew optimally at –8 to –12 bars at 30 C, but did not grow at 35 C, regardless of the water potential. All optimal water potentials were lower than normal in common culture media (–1 to –2 bars). The responses recorded for the three pathogens match their ecological distribution in nature; i.e., Graminearum and Culmorum both cause foot rot of wheat in hot, dry soil, with Graminearum being associated with slightly hotter and drier soil than Culmorum. Gaeumannomyces graminis causes foot rot of wheat in cool, wet soils.