Sporulation and pathogenicity of an Australian isolate of wheat rust grown in vitro

Abstract

Colonies of Puccinia graminis Pers. f. sp. tritici Erikss. & Henn., race ANZ 126-6,7 were grown from uredospores on Czapek's mineral salts, 3% glucose, 0.1% Evans' peptone, plus defatted bovine serum albumen. Dikaryotic vegetative hyphae apparently developed from centers of germ tube anastomosis, without the formation of typical infection structures. Typical pigmented uredospores and teliospores were formed after 6 to 8 weeks growth. Both spore forms were coated with a layer of material which was visible under the scanning electron microscope and was not observed on uredospores grown on intact wheat leaves. The uredospores were capable of infecting the mesophyll of wheat leaves exposed by stripping back the lower epidermis. The possibility is considered that the surface coating of uredospores grown in vitro is related to their inability to infect intact leaves via the stomata.