Abstract :
A method is described for establishing isolates of Puccinia
recondita f. sp. tritici (causal agent of brown rust of
wheat) on detached seedling leaf segments. The method
was used to compare the responses of leaf segments and
intact seedling leaves for 28 differential genotypes inoculated
with eight rust isolates. Leaf segments were incubated
at two post-inoculation temperatures (17 and
23 C) and intact seedlings at 20-25 C. Reliable determinations
of isolate pathogenicity was obtained using
detached leaf segments of wheats with genes Lrl. Lr2a,
Lr3a, Lr3bg., Lr3ka, Lr9, Lr]5, Lrl9. Lr20, Lr24, Lr25.
Lr26, Lr28, and Lr30 at both post-inoculation temperatures,
and for wheats with genes Lr2b. Lr2c, Lrl7,
Lr23, Lr27 + Lr31 and LrH, at 23 C. Differences between
leaf segments and intact leaves for the remaining eight
differentials were attributed to inconsistent or poor
expression of genes in detached leaf segments. By repeating
tests with detached leaf segments, it was possible to
establish the pathogenicities of the isolates on all of these
differentials except those carrying Lrl3, Lrl4a, Lrl6 and
Lrl8. Potential uses and limitations of the technique in
studies of Puccinia recondita f. sp. tritici are discussed
Keywords :
infection type , pathotype , virulence , wheat brownrust , wheat leaf rust