Infection of adventitious roots of Agrostis palustris by Pythium species at different temperature regimes.
The pathogenicity of several isolates of Pythium spp. to the adventitious roots of A.[stolonifera] var. palustris was evaluated at high (35:24°C, light:dark) and low (24:13°, light:dark) temp. regimes. Isolates of P. graminicola-arrhenomanes, P. rostratum, P. torulosum, P. vanterpoolii and 1 unclassified species were evaluated. All isolates of all species infected roots. Some isolates of P. graminicola-arrhenomanes (PGA-5), P. torulosum (PT-1, PT-2, PT-3, PT-5), P. vanterpoolii (PV-1) and an unclassified species (UP-1) infected roots and decreased DW at both the high and low temp. regimes. Other isolates of P. graminicola-arrhenomanes (PGA-1, PGA-2, PGA-4, PGA-6, PGA-7) and P. torulosum (PT-4) infected roots and decreased DW only at high temp. Isolate PGA-7 of P. graminicola-arrhenomanes also stimulated plant growth at low temp. The remaining isolates of P. graminicola-arrhenomanes (PGA-3), P. rostratum (PR-1) and P. vanterpoolii (PV-2) infected roots and decreased DW only at the low temp. Infection of roots was limited to root hairs, root tips and epidermal and cortical tissues. The observations are discussed relative to the function of Pythium spp. as minor root pathogens and their potential function in disease complexes.