VIEW ARTICLE

Effect of Soil Water Potential on Disease Incidence and Oospore Germination of Pythium aphanidermatum. M. E. Stanghellini, Associate Professor, Department of Plant Pathology, University of Arizona, Tucson 85721; T. J. Burr, Graduate Research Assistant, Department of Plant Pathology, University of Arizona, Tucson 85721. Phytopathology 63:1496-1498. Accepted for publication 4 June 1973. DOI: 10.1094/Phyto-63-1496.

Oospores of Pythium aphanidermatum germinated directly in asparagine-amended soils maintained at soil moisture levels ranging from saturation to –15 bars matric water potential. Percentage oospore germination and germ-tube growth rates were reduced at the lower soil moisture levels. Colonization of alfalfa seeds, sown in soil containing a natural population of 80 viable oospores of P. aphanidermatum/g soil, occurred at all soil moisture levels except –15 bars matric potential. Data indicate that wet soil conditions favor the activity of Pythium by increasing nutrient availability for oospore germination.