Effect of Salinity Stress on Development of Pythium Blight of Agrostis palustris

Abstract

Salinity stress predisposed cultivar Penncross creeping bentgrass to cottony blight caused by Pythium aphanidennatum at two temperature regimes. At 25-32 C, complete necrosis of all inoculated plants occurred at electrical conductivity (Ec) levels from 4.3-7.1 ds/m in 2 days, whereas at Ec levels of 0.5-2.8 ds/m death occurred within 3 days. At 25-27 C, complete necrosis of all inoculated plants occurred at Ec levels from 4.3-7.1 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. Mycelia' 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.