The Role of Wild and Cultivated Grasses in the Hybridization of Formae Speciales of Puccinia Graminis

Although Berberi8 vulgari8, the alternate host of Puccinia gramini8, occurs rarely on the Australian mainland, the present studies show that native and cultivated grasses can play an effective part in the evolution of new strains of this pathogen. Agropyron 8cabrum and Hordeum leporinum appear to be important as sources of somatic hybrids involving P. graminiB f. sp. tritici and P. graminiB f. sp. 8ecali8. On the Darling Downs of Queensland the former grass species was found to be infected by more than 25 different hybrid strains. The principles governing hybridization between these two formae speciales of P. gramini8 may also be applicable to corresponding events between other rusrs.