A Database for Triticeae and Avena
JOHN INNES CENTRE
Norwich Research Park, Colney, Norwich NR4 7UH, United Kingdom.
We have recently completed a industrial LINK project on Breeding
for Resistance to S. tritici, supported by the Department
for the Environment, Food and Rural Affairs and six plant breeding
companies with U.K. interests. We have discovered that many of
the most widely-used sources of Septoria resistance in world wheat
breeding have the gene Stb6. The widespread distribution
of this gene limits the scope for transgressive segregation of
resistance and points to the need to use a greater range of resistance
genes. We have identified and mapped four new genes for resistance
to Septoria, Stb9 in several European spring wheat cultivars;
Stb10 and Stb12 in Kavkaz-K4500, an especially important
source of resistance; and Stb11 in TE9111, a Portuguese
breeding line that is the most resistant modern European wheat
known. Through an associated genetic analysis, we also have shown
that many genes, dispersed over the chromosomes of wheat, promote
partial resistance to Septoria.
We are now beginning a new LINK project, Improved Resistance
to S. tritici in Superior Varieties, in which we will quantify
the contributions to disease reduction in the field of Septoria
resistance genes identified in the previous LINK project and investigate
the interaction of Septoria resistance with other plant
traits important to U.K. and European wheat breeders.
Paul Nicholson, Liz Chandler, Natalie Chapman, Richard Draeger,
Nick Gosman, Wendy Monger, Andy Steed, and Martha Thomsett.
The study of the genetic basis of resistance to FHB in winter
wheat is continuing. The resistance of Arina and WEK0609 has
been analyzed and mapping and QTL analysis of resistance of these
populations is nearing completion. Fine mapping of the T.
aesvivum subsp. macha 4A FHB resistance is ongoing
and is being combined with gene-expression studies to identify
candidate resistance genes. Host-pathogen interaction is being
studied in detail for infection of Arina and Riband by F. culmorum.
Expression of wheat PR genes and fungal toxin-biosynthesis genes
is being determined for the two hosts during infection and colonization
of wheat spikes. A collaborative project is underway to assess
the level of FHB resistance among U.K. wheat cultivars and to
introduce and pyramid FHB from diverse sources to improve the
level of resistance among winter wheat cultivars in the U.K.
SSR analysis of U.K. and European wheats indicates the absence
of any of the common FHB-resistance QTL of Chinese origin among
this germ plasm lines are being developed to determine the combining
ability of selected FHB QTL to identify the best combinations
for use in breeding programs. Molecular diagnostics are being
used to study effects of, and interactions between, Fusarium isolates
of different chemotype on different cereal hosts. Molecular diagnostics
also have revealed that the U.K. wheat crop is exposed to a more
diverse array of chemotypes than that in the U.S. In addition
to studies on FHB, mapping and molecular studies of two eyespot
resistance genes (Pch1 and Pch2) are continuing.
Lesley A. Boyd, Clare Lewis, Muge Sayar, James Melichar, Luke
Jagger, and Hale Tufan.
A number of QTL for APR to yellow (stripe) rust have been identified
in the U.K. wheat cultivar Claire and within the Claire pedigree.
Mapping work also is underway to identify the QTL for a source
of partial APR to yellow rust in the cultivar Guardian.
The dissection of genetic biodiversity for yellow rust APR in
U.K. wheat cultivars will be extended to include a comparison
to biodiversity in Turkish wheats as part of a new collaboration
between H-J. Braun (CIMMYT, Turkey) and M.T. Sayar (Bogazici University,
James Melichar and Lesley A. Boyd.
A number of mutants, generated by gamma-radiation in the U.K.
cultivar Guardian, were originally selected in the field for enhanced
resistance to yellow rust. This enhanced resistance was shown
not to express in seedlings, but to be developmentally regulated,
expressing at adult plant growth stages. A microscopic-staining
procedure has been developed in the group that allows detailed
histological examination of yellow rust development in adult plant
tissue. Using this methodology, the partial APR in Guardian has
been shown to restrict sporulation, but this resistance is not
associated with the release of hydrogen peroxide by the plant,
a response common to race-specific resistance. However, the enhancement
of resistance, due to mutation, is associated with the production
of hydrogen peroxide.
In addition to the enhancement of resistance to yellow rust
in adult plants, a number of the mutants also exhibit enhanced
resistance to leaf rust and/or powdery mildew. Mapping populations
have been developed for Guardian and two of the mutants, and these
will be used to locate both the partial yellow rust APR in Guardian,
the mutations responsible for the enhancement of yellow rust resistance,
and the mutations conferring resistance to leaf rust and powdery
Ruth MacCormack and Lesley A. Boyd.
A new program in the laboratory of L.A. Boyd examines the early
stages of yellow rust infection to determine what factors optimize
infection efficiency of this fungal pathogen. Having identified
the physiological factors that the pathogen requires to successfully
enter the plant through open stomata, phenotypic screens will
be established to look for genetic variation within wheat for
Simon Orford, Pauline Stephenson, and Robert Koebner.
As part of our contribution to the Wheat Genetic Improvement
Network (see AWN 50:192), we are developing an immortal population
of EMS-mutagenized spring wheat cultivar Paragon by single-seed
descent. The initial M1 population numbered ~ 3,500 individuals,
from which two M2 seeds/M1 plant were sown. The population is
currently (spring-summer 2005) being advanced from M3 to M4 as
~ 7,000 independent lines. From the M6, we intend to field multiply
the lines and make them available to collaborators for gene discovery
and functional gene analysis.
Andrew Bottley and Robert Koebner.
Our SSCP-based analysis of patterns and frequency of homoeolog
silencing in wheat continues to surprise. We are working with
single-copy EST sequences located to homoeologous group under
the NSF wheat EST program, comparing amplicon patterns generated
from cDNA templates from both root and leaf tissue. Globally,
around 15 % of the loci are nontranscribed, but we have noted
a significant frequency of cases where in the presence of additional
doses of a chromosome (as are present in the nullisomic-tetrasomic
stocks), a homoeolocus silenced in the euploid condition is transcribed.
To avoid noncomparability between genomic and cDNA profiles,
we are using the rice genome sequence to target amplicons lacking