Infection of adventitious roots ofAgrostis palustrisbyPythiumspecies at different temperature regimes

摘要

Pathogenicity of several isolates ofPythiumspecies to the adventitious roots ofAgrostis palustriswas evaluated at high (35:24, light:dark) and low (24:13 °C, light:dark) temperature regimes. Isolates ofP.graminicola–arrhenomanes,P.rostratum,P.torulosum,P.vanterpoolii, and one unclassified species were evaluated. All isolates of all species infected roots. Some isolates ofP.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 dry weight at both the high and low temperature regimes. Other isolates ofP.graminicola–arrhenomanes(PGA-1, PGA-2, PGA-4, PGA-6, PGA-7) andP.torulosum(PT-4) infected roots and decreased dry weight only at the high temperatures. Isolate PGA-7 ofP.graminicola–arrhenomanesalso stimulated plant growth at low temperatures. The remaining isolates ofP.graminicola–arrhenomanes(PGA-3),P.rostratum(PR-1), andP.vanterpoolii(PV-2) infected roots and decreased dry weight only at the low temperatures. Infection of roots was limited to root hairs, root tips, and epidermal and cortical tissues. The observations are discussed relative to the function ofPythiumspecies as minor root pathogens and their potential function in disease complexes.Key words: disease complexes, infection, minor pathogens, pathogenesis, pathogenicity,Pythium arrhenomanes,P.graminicola,P.graminicola–arrhenomanes,P.rostratum,P.torulosum,P.vanterpoolii.