Mago, R., Tabe, L., Vautrin, S., Šimková, H., Kubaláková, M., Upadhyaya, N., Berges, H., Kong, X., Breen, J., Doležel, J., Appels, R., Ellis, J.G., Spielmeyer, W.
BMC PLANT BIOLOGY
14:
379,
2014
Keywords:
Adult plant resistance (APR), Map-based cloning, Sr2, Germin-like proteins (GLPs), Wheat stem rust, Puccinia graminis, Physical mapping, Gene expression
Abstract:
Background: The adult plant stem rust resistance gene Sr2 was introgressed into hexaploid wheat cultivar (cv) Marquis
from tetraploid emmer wheat cv Yaroslav, to generate stem rust resistant cv Hope in the 1920s. Subsequently, Sr2 has
been widely deployed and has provided durable partial resistance to all known races of Puccinia graminis f. sp. tritici. This
report describes the physical map of the Sr2-carrying region on the short arm of chromosome 3B of cv Hope and
compares the Hope haplotype with non-Sr2 wheat cv Chinese Spring.
Results: Sr2 was located to a region of 867 kb on chromosome 3B in Hope, which corresponded to a region of 567 kb in
Chinese Spring. The Hope Sr2 region carried 34 putative genes but only 17 were annotated in the comparable region of
Chinese Spring. The two haplotypes differed by extensive DNA sequence polymorphisms between flanking markers as
well as by a major insertion/deletion event including ten Germin-Like Protein (GLP) genes in Hope that were absent in
Chinese Spring. Haplotype analysis of a limited number of wheat genotypes of interest showed that all wheat genotypes
carrying Sr2 possessed the GLP cluster; while, of those lacking Sr2, some, including Marquis, possessed the cluster, while
some lacked it. Thus, this region represents a common presence-absence polymorphism in wheat, with presence of the
cluster not correlated with presence of Sr2. Comparison of Hope and Marquis GLP genes on 3BS found no polymorphisms
in the coding regions of the ten genes but several SNPs in the shared promoter of one divergently transcribed GLP gene
pair and a single SNP downstream of the transcribed region of a second GLP.
Conclusion: Physical mapping and sequence comparison showed major haplotype divergence at the Sr2 locus between
Hope and Chinese Spring. Candidate genes within the Sr2 region of Hope are being evaluated for the ability to confer
stem rust resistance. Based on the detailed mapping and sequencing of the locus, we predict that Sr2 does not belong to
the NB-LRR gene family and is not related to previously cloned, race non-specific rust resistance genes Lr34 and Yr36.
Fulltext: contact IEB authors
IEB authors: Jaroslav Doležel,
Marie Kubaláková,
Hana Šimková
