Disease and Stress Biology Department, John Innes Centre, Norwich
Research Park, Colney Lane, Norwich, NR4 7UH, UNITED KINGDOM
In Europe, the need to understand and use host plant resistance to
septoria tritici blotch (STB) has
assumed new urgency with the widespread development of resistance to QoI
(strobilurin and related) fungicides in the STB pathogen, Mycosphaerella
graminicola. We have investigated factors that contribute to reducing STB
levels among wheat cultivars in field conditions, including resistance to
specific isolates of M. graminicola and aspects of plant development and
morphology that contribute to disease escape. This has allowed the
identification of cultivars which are useful sources of isolate-non-specific,
foliar resistance to STB for wheat breeding.
A total of 226 wheat genotypes were studied, including cultivars grown
in the UK and other lines relevant to UK breeding programmes, including
progenitors of current cultivars. Eleven field trials were carried out at eight
sites over three years, in which STB and escape factors were scored. All 226
lines were screened with single isolates to identify the presence of specific
resistance genes using the detached leaf technique (Arraiano et al. 2001b). A sub-set of 98 lines
were scored with 121 microsatellite markers covering all 21 chromosomes.
At least two specific resistance genes were associated with significant
reduction of STB in the set of wheat genotypes. One of these was the most
important predictor of resistance other than height to flag leaf and heading
date. The development of a model which combines escape factors (heading date,
plant height and leaf spacing) with specific resistances that are correlated
with disease levels has enabled us to detect cultivars with greater resistance
to STB than the model predicts. These are likely to be new sources of STB
resistance for wheat breeding programmes in the UK and elsewhere. Other regions
of the genome that may contain hitherto unknown resistance genes were
identified by linkage to microsatellite markers in an association genetic
analysis.
This research is providing breeders with knowledge about the potential
value of genes for resistance to STB and about previously unidentified sources
of resistance within the pool of wheat germplasm adapted to UK conditions. This
is expected to lead to improved selection of wheat varieties with resistance to
STB and in due course, to a sustained, gradual improvement in the resistance of
European wheat varieties to STB and thus to reduced need for fungicides to
control this disease.
Acknowledgements: This research was done in collaboration with Advanta Seeds UK, Cebeco
Seed Innovations, Elsoms Seeds, Nickerson, SW Seed and Syngenta Seeds through
the Sustainable Arable LINK Programme.
Reference:
Arraiano LS, Brading PA, Brown JKM, 2001. A detached seedling leaf technique to study resistance to Mycosphaerella graminicola (anamorph Septoria tritici) in wheat. Plant Pathology 50: 339-346.