A SIMPLE AND RELIABLE METHOD FOR GROWING THE WHEAT-STEM RUST FUNGUS, PUCCINIA-GRAMINIS F-SP TRITICI, IN LIQUID CULTURE

A simple and reliable method for growing the wheat stem rust fungus axenically in liquid culture has been developed. Uredospores of Puccinia graminis f. sp. tritici, freshly harvested from susceptible wheat leaves, were washed with sterile 0·1% sodium dodecyl sulphate and sterile water prior to inoculation into a filter sterilized medium. Optimal fungal growth was obtained at pH 6 and at a temperature of 23 °C, in the dark, with gentle shaking. Formation of infection structures could be induced by application of a heat shock or the addition of acrolein. Production of uredospores and, eventually, teleutospores, was induced by reducing the nutrient content of the medium to 5% of the normal level or reducing the pH of the medium. Growth of the colonies was limited to a period of about a 4 weeks and attempts at subculturing were unsuccessful. Vegetative colonies grown in liquid culture were infectious on leaves from susceptible, but not resistant wheat cultivars, provided the host epidermis was removed before inoculation. Occasionally, a non-infectious subculturable white fluffy mycelium developed after several months in culture. © 1993 Academic Press, Inc.