8th INTERNATIONAL WHEAT CONFERENCE

ChARACTeRIzATIoN of STem RuST ReSISTANT geNeS
IN WILd TeTRAPLoIdS
Alwan E 1, 2 *, Ogbonnaya FC 2 , Ayele B 3 , Nazari K 2 ,
Abdalla O 2 , Yahyaoui A 2 , and Hakim SH 1 .
1 Aleppo University, Faculty of Agriculture, Field Crops Department, Aleppo, Syria
2 International Centre for Agricultural Research in the Dry Areas, PO Box 5466, Aleppo, Syria.
3 Ethiopian Institute of Agricultural Research (EIAR), Box 2003, Addis Ababa, ETHIOPIA
4 ICARDA-CIMMYT Wheat Improvement Program, Box 5466, Aleppo, Syria
E-mail Address of presenting author: E.Alwan@cgiar.org
Stem rust (puccinia graminis f. sp. Tritici) is one of the deadliest fungal diseases of wheat,
which until the mid 1950s posed a tremendous threat to wheat production worldwide.
The disease has been brought under control through the deployment of genetic resistance
using mostly major genes transferred from cultivated, rye and wild relatives of wheat. The
emergence of a new devastating race commonly known as Ug99 designated “TTKS”, virulent
on most of the widely used genes, with reported yield losses in Kenya and Ethiopia
ranging from to 20-50% renewed the threat to wheat production.
Currently, about 50 stem rust resistance Sr genes have been identified and mapped to specific
chromosome. Among Sr genes identified, only few remain effective to Ug99. Most
of these genes originated from diploid, tetraploid and hexaploid wheat. Use of molecular
markers would greatly enhance the effective deployment of the resistance genes. Amongst
the mapped Sr genes, molecular markers have been identified linked to some of the Ug99
effective resistance genes.
This study reports on characterization of 72 wild tetraploids showing adult plant resistance
(APR) using available molecular markers linked to Ug99 resistance genes in an attempt
to identify potentially new resistance genes. The tetraploids wheat accessions used
in this study were identified based on seedling and adult plant test under a 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). Out of the accessions tested, 36 accessions showed
the diagnostic fragment associated with Sr2-linked SSR markers. Further, 6 and 11 accessions
possessed the DNA fragment associated with Sr22 and Sr36 resistance genes respectively.
About 41 % of the wild tetraploid accessions do not possess either SSR or STS haplotypes
associated with the currently mapped Ug99 effective genes that we investigated in
the current study. Our preliminary results indicate that wild tetraploid accessions could
provide potentially new sources of durable stem rust resistance in wheat.
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