Influence of irrigation on survival of Poa pratensis infected by Ustilago striiformis and Urocystis agropyri

Abstract

Irrigation increased the number of surviving plants of Poa pratensis 'Merion' infected with Ustilago striiformis (stripe smut) and Urocystis agropyri (flag smut) and stimulated the production of healthy shoots from infected plants. These effects were more pronounced with plants infected by U. striiformis. Nonirrigated plants infected by U. agropyri had died by the end of the second growing season: irrigation increased the survival of some U. agropyri infected plants to a third growing season and increased the survival of many U. striiformis infected plants for the same period. The number of healthy plants established from irrigated plants infected by U. striiformis also was much greater than those established from plants infected by U. agropyri. The pattern of development for healthy shoot production from infected plants differed for the respective pathogens. The reaction of U. striiformis and U. agropyri to irrigation suggests that U. agropyri is the more destructive of the two pathogens. The production of healthy shoots from infected plants may provide a means for evaluation of P. pratensis for resistance to U. striiformis.