Genetics of resistance of wheat to septoria tritici blotch.
The research described in this týesis was focused on achieving a better understanding
of the genetics of resistance of wheat to septoria tritici blotch (Mycosphaerella
Firstly, a detached leaf technique that could be a useful complement to field trials and
an alternative to whole seedling assays in assessing cultivar resistance and
investigating the genetics of the host-pathogen interaction was developed. Sets of
inter-varietal substitution lines, developed at the John Innes Centre, involving known
and possible sources of resistance to septoria tritici blotch, were tested with several
single-pycnidium isolates in both the seedling and the adult plant stage. Two specific
resistance genes were identified on chromosomes of `Synthetic 6x' and `Bezostaya 1'.
A resistance gene, named Stb5, was identified using the M. graminicola isolate
IP094269 and mapped on the short arm of chromosome 7D of `Synthetic 6x'.
`Bezostaya I's specific resistance gene to IP0323 seems to be located in the same
region as Stb6, and is indeed likely to be the same gene. `Bezostaya 1' and `Cappelle
Desprez' also seemed to carry components for partial resistance. Triticum macha
resistance to septoria tritici blotch on the other hand was both of a specific and isolatenon-
specific nature. The specific components carried by T. macha seemed to be the
Stb6 gene and an additional resistance gene, but it was not possible to identify their
To evaluate the relationship of heading date and plant height components to severity
of septoria tritici blotch, an F6 single seed population of `Apollo' x `Thesee' was
studied in natural conditions. Septoria tritici blotch levels were substantially lower in
later-heading than in earlier-heading lines. Total plant height had comparatively little
effect on disease severity, but increased distance between the two upper leaves
increased disease levels. `Apollo' seems to carry partial resistance involving more
than one QTL.