Septoria and Stagonospora Diseases of Cereals - CIMMYT ...

ecombination plays in the
population dynamics. This level of
variation may have implications for
the cereal plant breeding and
selection program if it is a reflection
of the potential variability for
aggressiveness in the pathogen. If
the level of genotypic variation does
reflect the level of variation in
aggressiveness, selecting resistance
using the widest possible range of S.
nodorum isolates would be desirable.
The most practical method to
screen breeding lines for a wide
selection of S. nodorum isolates is to
use straw from previously infected
wheat as a source of inoculum
(Holmes and Colhoun, 1975).
Previous work investigating the
effect of the host genotype upon the
selection of S. nodorum provided no
evidence of specialization of the
pathogen with the host cultivar
(Keller et al., 1997b) according to
neutral RFLP markers. It would also
be unnecessary to use straw from
numerous sites, as the genotypic
variation encountered at a single site
can account for as much as 95% of
the total genotypic variation within a
population (Keller et al., 1997b).
Using straw from a collection of
cultivars and from a number of sites
may be unnecessary, as it would
provide only a modest increase in
the overall genotypic diversity.
References
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Variation in pathogenicity, virulence
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Ascospores as primary inoculum of
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89
Keller, S.M., M.S. Wolfe, J.M.
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