New Zealand Journal of Crop and Horticultural Science abstracts
Adult plant resistances to Puccinia recondita f. sp. tritici in
wheat
R. F. PARK
R. A. McINTOSH
University of Sydney
Plant Breeding Institute
107 Cobbitty Rd
Cobbitty, NSW 2570
Australia
Abstract Tests with adult plants in the greenhouse confirmed
virulence in Australasian populations of Puccinia recondita f. sp.
tritici for the adult plant resistance genes Lr12, Lr13,
and Lr22b. Virulence for Lr22b has been very common since at
least the early 1960s, and it is likely that this gene will be of limited use
in breeding for leaf rust resistance. The frequencies of virulence for
Lr12 and Lr13 declined during the period 1989-92. Virulence for
Lr12 probably originated in northern New South Wales and/or Queensland
following the release of cultivar `Timgalen' in 1967. Pathotypes virulent for
this gene predominated in this region during 1975-87, after which they were
gradually replaced by an apparently more aggressive group of pathotypes
avirulent for Lr12. The gene Lr13, in combination with certain
seedling resistance genes, remained effective against all pathotypes isolated
in pathogenicity surveys conducted before 1992. It is proposed that Lr12
could be deployed in a similar manner. Six genes conferring adult plant
resistance to wheat leaf rust were placed into four groups on the basis of the
earliest growth stage at which they could be detected under controlled
greenhouse conditions. Lr13 was detected in primary seedling leaves of
plants inoculated 2 weeks after sowing. Resistances conferred by other genes
were detected in plants inoculated 3 weeks after sowing (Lr37), 5 weeks
after sowing (Lr12, Lr22a, and Lr35), or 9 weeks after
sowing (Lr22b).
Keywords Puccinia recondita; Triticum aestivum;
wheat leaf rust; adult plant resistance; virulence
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