Pathogenic variability in Puccinia hordei in Australia
1992
Park, R.F. (Sydney Univ., Cobbitty (Australia). Plant Breeding Inst.) | Cotterill, P.J. | Rees, R.G.
The virulence combinations for UN Races 16 and 14 of Puccinia hordei (Pa2, Pa4, and Pa8, and Pa, Pa2, Pa4, and Pa8 respectively;) were not detected in the present study, despite the fact that these rusts were considered to predominate prior to about 1985. Reasons for this are not clear, but it is possible that the number of pre-1985 samples examined was insufficient to be fully representative of the population. The occurrence of a group of pathotypes during the early 1980's which were distinct from pt. 243 may have resulted from the introduction of an exotic pathotype into Australia, and subsequent development of related pathotypes through single-step mutations. Alternatively, it is possible that this group originated from sexual recombination. Infected plants of the alternate host (Ornithogalum umbellatum) were located in a small region of South Australia. Another distinctive form, pt. 20, was recovered from two samples collected from Victoria and South Australia and may also have arisen through sexual recombination. Most Australian barley cultivars are susceptible to at least one of the pathotypes of P.hordei identified. Virulence for the genes Pa3 and Pa7 was not detected; hence these genes could be deployed in new cultivars. For the longer term, other sources of resistance should be sought since virulence to both genes has been detected in other barley-growing regions of the world.
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