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Ecology and Epidemiology

Effect of Salinity Stress on Development of Pythium Blight in Agrostis palustris. S. L. Rasmussen, Research assistant, Department of Plant Pathology, University of Arizona, Tucson 85721; M. E. Stanghellini, professor, Department of Plant Pathology, University of Arizona, Tucson 85721. Phytopathology 78:1495-1497. Accepted for publication 15 July 1988. Copyright 1988 The American Phytopathological Society. DOI: 10.1094/Phyto-78-1495.

Salinity stress predisposed cultivar Penncross creeping bentgrass to cottony blight caused by Pythium aphanidermatum at two temperature regimes. At 2532 C, complete necrosis of all inoculated plants occurred at electrical conductivity (Ec) levels of 4.37.1 decisiemens (ds) per meter in 2 days, whereas at Ec levels of 0.52.8 ds/m, death occurred within 3 days. At 2527 C, complete necrosis of all inoculated plants occurred at Ec levels of 4.37.1 ds/m within a period of 5 days; no death was observed in control or inoculated plants at an Ec level of 0.5 ds/m. Increased salinity levels apparently affected the bentgrass rather than P. aphanidermatum. Mycelial growth rate of the fungus was increased only slightly by salinity levels up to 7.1 ds/m. Zoospore production of P. aphanidermatum and two other species of Pythium decreased with increasing salinity levels up to 7.1 ds/m; production was completely inhibited at 14.2 ds/m.

Additional keywords: Pythium catenulatum, Pythium dissotocum.