Characterization of Stem Rust Resistant
Genes in Wild Tetraploids
Alwan E1,2, Ogbonnaya FC2*, Ayele B3, Nazari K2, Abdalla O2, Yahyaoui A4, and Hakim SH1 CGIAR
Aleppo University, Faculty of Agriculture, Aleppo, Syria. 2
ICARDA, PO Box 5466, Aleppo, Syria
Ethiopian Institute of Agricultural Research, Box 2003, Addis Ababa, Ethiopia. ICARDA-CIMMYT Wheat Improvement Program, PO Box 5466, Aleppo, Syria
*Corresponding author: F.Ogbonnaya@cgiar.org
A total of 73 wild tetraploid wheat accessions showing adult plant resistance (APR)
were analyzed using molecular markers linked reportedly to wheat stem rust race
Ug99 resistance genes. The wheat accessions were identiﬁed based on seedling and 150
adult plant test under heavy Ug99 inoculation conducted at Debre Zeit, Ethiopia. The
accessions were haplotyped for stem rust resistance genes Sr2, Sr22, Sr26, Sr36,
Sr40 using linked microsatellite (SSR) and diagnostic sequence tagged sites (STS).
Of the accessions tested, 2 accessions showed the diagnostic fragment associated
Sr2 Sr2 120 bp
with Sr2-linked SSR markers; while 1, 7, and eight accessions possessed the DNA
fragment associated with Sr22, Sr36, and Sr40 resistance genes respectively . About
75% of the wild tetraploid accessions do not possess either SSR or STS haplotypes
associated with the currently mapped Ug99 effective genes that we investigated. Our Figure 1. PCR ampliﬁcation of wild tetraploids with Sr2 linked marker.
preliminary results indicate that wild tetraploid accessions could provide potentially
new sources of durable stem rust resistance in wheat.
Stem rust (caused by Puccinia graminis f. sp. tritici Eriks. & E. Henn) is one of the
deadliest fungal diseases of wheat, which until the mid 1950s posed a tremendous threat
to wheat production worldwide. The disease was brought under control through the Control 150 bp
deployment of genetic resistance using mostly major genes transferred from cultivated Marker
rye and wild relatives of wheat until recently. However, the threat was renewed by the Figure 2. PCR ampliﬁcation of wild tetraploids with Sr22 linked marker.
emergence of a new race commonly known as Ug99 designated “TTKS” (Singh et al.
2006), virulent on most of the widely used genes, with reported yield losses in Kenya
and Ethiopia ranging from to 20-50%. One accession of T. turgidium subsp dicoccoides with the phenotype SS/AMR also
Use of molecular markers would enhance the effective deployment of resistance genes. possessed the DNA fragment linked to Sr22 (Fig. 2).
Currently, about 50 stem rust resistance Sr genes have been identiﬁed and mapped to
speciﬁc chromosome (McIntosh et al. 2008). Amongst the mapped Sr genes, molecular Additionally, six accessions of T.timopheevii var. timopheevii, and one of T. turgidium
markers have been identiﬁed linked to some Ug99 effective resistance genes. The subsp dicoccoides which displayed seedling susceptibility and adult plant resistance
objective of this study was to determine the frequency of the DNA markers linked with (SS/AR) possessed the SSR haplotype linked to Sr36. Further, three accessions of T.
TTKS effective resistance genes, Sr2, Sr22, Sr26, Sr36, and Sr40 in wild tetraploids, turgidium subsp dicoccon, two of T. turgidium subsp dicoccoides, two of T.timopheevii
in order to identify those carrying genes likely different from those previously reported. var. timopheevii and one accession of T. turgidium subsp turanicum possessed the
SSR fragment linked to Sr40 gene. However, none of the tested accessions showed
the presence of the DNA fragment linked to Sr26.
Materials and Methods
In total, about 75% of the wild tetraploid accessions do not possess either SSR or
The wild tetraploid wheat accessions used in this study consisted of the following
STS haplotypes associated with the currently mapped Ug99 effective genes that we
investigated. The results indicate that wild tetraploids of wheat could provide potentially
T. turgidum subsp. dicoccoides 28 T. turgidum subsp. carthlicum 6
new sources of durable stem rust resistance in wheat. These are further being genotyped
T. turgidum subsp. dicoccon 18 T. turgidum subsp. turanicum 4
as more markers become available to ensure that only those with new APR genes are
T. timopheevii subsp. timopheevii 10 T.timopheevii var araraticum 4
used in germplasm enhancement of durum and bread wheat.
T. turgidum subsp. polonicum 1 T. turgidum subsp. turgidum 2
Eight linked and diagnostic SSR and STS markers were chosen for haplotyping ﬁve
Table 2. Distribution of diagnostic markers linked to stem rust resistance
major stem rust resistance genes located on A and
genes Sr2, Sr22, Sr26 and Sr36 in wild Triticum species
B genomes (Table 1). PCR reaction was carried
out as previously reported by the authors. A group Gene
of monogenic lines having the above-mentioned Species sr2 sr22 sr26 sr36 sr40 No. of lines
major genes in addition to some lines previously T. turgidium subsp dicoccon 3 3
characterized and known to possess Sr genes were
T. turgidium subsp dicoccoides 2 1 1 1 5
used as checks in this study.
T. turgidium subsp turgidium 1 1
Results and Discussion T. turgidium subsp turanicum 1 1
Table 2 summarizes the results of charactering wild T.timopheevii var timopheevii 6 2 8
Triticum species with Sr linked and/or diagnostic
markers. Among 73 accessions, two accessions (T.
turgidium subsp dicoccoides and T. turgidium subsp
turgidium) which displayed seedling susceptibility
and adult plant moderate resistance (SS/AMR)
showed the Sr2 haplotype (Fig. 1).
Mago R, Bariana HS, Dundas IS, Spielmeyer W, Lawrence GJ, Pryor AJ, Ellis JG (2005) Development
of PCR markers for the selection of wheat stem rust resistance genes Sr24 and Sr26 in diverse wheat
Table 1. Sr stem rust SSR –STS markers liked to Ug99 effective genes germplasm. Theor Appl Genet 111:496-504
located on AB genome. McIntosh, RA, Yamazaki Y, Dubcovsky J, Rogers WJ, Morris CF, Somers D, Appels R and Devos KM.
(2008) Catalogue of gene symbols for wheat. Gene symbols., In R. A.McIntosh, (ed.), http://wheat.pw.usda.
Fragment gov/GG2/Triticum/wgc/2008/GeneSymbol.pdf .
Gene Origin Locus Chromosome References
size (bp) Miranda LM, Perugini L, Srni´c G, Brown-Guedira G, Marshall D, Leath S, and Murphy JP (2007) Genetic
Mapping of a Triticum monococcum derived Powdery Mildew Resistance Gene in Common Wheat. Crop
Sr2 T. turgidum Xgwm533 120 3BS Sci 47:2323-2329.
Xbarc133 117 Spielmeyer et al. 2003 Singh RP, Hodson DP, Jin Y, Huerta-Espino J, Kinyua MG, Wanyera R (2006) Current status, likely
migration and strategies to mitigate the threat to wheat production.
T. monococcum ssp. Spielmeyer W, Sharp PJ, Lagudah ES (2003) Identiﬁcation and Validation of Markers Linked to 18 Broad-
Sr22 Xcfa2019 235 7AL Miranda et al., 2007
boeoticum Spectrum Stem Rust Resistance Gene Sr2 in Wheat (Triticum aestivum L.). Crop Sci 43:333-336.
Xcfa2123 245 Tsilo TJ, Jin Y, Anderson JA (2008) Diagnostic Microsatellite Markers for 1 the Detection of Stem Rust
Resistance Gene Sr36 in Diverse Genetic Backgrounds of Wheat. Crop Sci 48:253-261.
Sr26 Lophopyrum elongatum Sr26#43 207 6AL Mago et al., 2005 Yu L-X, Z. Abate Z, Anderson JA, Bansal UK, Bariana HS, Bhavani S, Dubcovsky J, Lagudah ES, Liu
S, Sambasivam PK, Singh RP, Sorrells ME (2009) Developing and Optimizing Markers for Stem Rust
Poster Design Abdurrahman Hawa
Sr36 T. timopheevi Xwmc477 187 2BS Tsilo et al., 2008 Resistance in Wheat. Proceedings of Borlaug Global Rust Initiative. C.D. Obregon, Mexico, 2009: P39-56
T. timopheevii ssp.
Sr40 Xgwm344 2BS Yu et al., 2009 Staff of ICARDA’s biotechnology and genetic resources units, Ethiopian Institute for Agricultural Research,
armeniacum Durable Rust Resistance in Wheat Project, Cornell University.