VIEW ARTICLE

Ecology and Epidemiology

Effect of Soil Water Matric Potential on Resistance to Fusarium oxysporum f. sp. medicaginis in Alfalfa. Gary Emberger, Former graduate student, Department of Plant Pathology, North Carolina Agricultural Research Service, Raleigh 27650, now assistant professor, Department of Natural Sciences, Messiah College, Grantham, PA 17027; Ronald E. Welty, research plant pathologist, Tobacco Research Laboratory, Forage Research Unit, Agricultural Research Service, U.S. Department of Agriculture, Oxford, NC 27565, Present address: USDA-ARS, Department of Botany and Plant Pathology, Oregon State University, Corvallis, OR 97331. Phytopathology 73:208-212. Accepted for publication 28 July 1982. This article is in the public domain and not copyrightable. It may be freely reprinted with customary crediting of the source. The American Phytopathological Society, 1983. DOI: 10.1094/Phyto-73-208.

Yields of uninoculated alfalfa cultivars Moapa (resistant) and Narragansett (susceptible) and Moapa inoculated with Fusarium oxysporum f. sp. medicaginis increased with increased soil moisture. Yield of inoculated Narragansett plants was less than that of uninoculated plants and did not increase in response to increased soil moisture. Severity of Fusarium wilt was not increased for either cultivar by increased soil moisture in greenhouse experiments. During the first 4 wk following inoculation in an outdoor experiment, the number of dead plants of Narragansett alfalfa was significantly larger in wet soil than in moist soil. However, by 8 wk, this difference was no longer observed. Although increased soil moisture may have an effect on the initial rate of Fusarium wilt development, no evidence was found that it altered the basic characterization of Moapa and Narragansett as cultivars resistant and susceptible, respectively, to Fusarium wilt.