Biology of the Acacia gall rust, Uromycladium tepperianum

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Abstract
Germinating teliospores of Uromycladium tepperianum formed penetration pegs, which directly penetrated host epidermal cells, on the tip cell of three‐celled germ tubes. Diploid nuclei within teliospores appeared to divide soon after germination commenced. Only one of the daughter nuclei moved out of the teliospores with the developing germ tubes. Reactions of seedlings inoculated with teliospores from different host species and differences in teliospore dimensions indicated that distinct genotypes of U. tepperianum adapted to particular host species occur in Australia. Limited hyphal growth occurred in two of 20 African Acacia spp. inoculated with teliospores from Acacia saligna. Fungal development was, however, restricted by necrosis of surrounding host cells. U. tepperianum appears to be suitably host‐specific for use as a biological control agent against Ac. saligna, a weed in South Africa.