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ARS Home » Midwest Area » St. Paul, Minnesota » Cereal Disease Lab » Research » Publications at this Location » Publication #296446
Title: Genome-wide search of stem rust resistance loci at the seedling stage in durum wheat

Author
item LETTA, TESFAYA - Ethiopian Agricultural Research
item OLIVERA, PABLO - University Of Minnesota
item MACCAFERRI, MARCO - University Of Bologna, Italy
item Jin, Yue
item AMMAR, KARIM - International Maize & Wheat Improvement Center (CIMMYT)
item BADEBO, AYELE - Ethiopian Agricultural Research
item NOLI, ENRICO - University Of Bologna, Italy
item CROSSA, JOSE - International Maize & Wheat Improvement Center (CIMMYT)
item TUBEROSA, ROBERTO - University Of Bologna, Italy

Submitted to: The Plant Genome
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/9/2013
Publication Date: 3/18/2014
Citation: Letta, T., Olivera, P., Maccaferri, M., Jin, Y., Ammar, K., Badebo, A., Noli, E., Crossa, J., Tuberosa, R. 2014. Genome-wide search of stem rust resistance loci at the seedling stage in durum wheat. The Plant Genome. 7:1-13.

Interpretive Summary: Stem rust is a disease of wheat that can cause serious crop losses. The pathogen, Puccinia graminis f. sp. tritici, is known to rapidly evolve new virulence to resistance genes. A few genes in durum wheat remain effective against the highly virulent race Ug99 (TTKSK) and a mixture of durum-specific races. Association mapping (AM) was deployed on 183 elite durum wheat accessions tested under controlled conditions in order to identify quantitative trait loci (QTLs) for resistance to four highly virulent stem rust races. A number of chromosome regions were significantly associated with resistance to these stem rust races based on seedling tests. The present study demonstrates that stem rust resistance in durum association panel is governed in part by shared loci and in part by race-specific ones. Combining the results of this study with those on adult plant resistance in the field will provide valuable indications to select suitable parental lines for further improving stem rust resistance of durum wheat. While some markers were linked to known Sr genes (e.g. Sr9, Sr13 and Sr14), other significant markers were located in chromosome regions where Sr genes have not been previously reported. The allelic variation identified at these novel QTLs provides additional opportunities to deploy marker-assisted selection to improve adult plant resistance to stem rust in durum wheat. This research will benefit wheat breeders in utilizing Ug99 resistance genes to improve stem rust resistance in durum.

Technical Abstract: Puccinia graminis f. sp. tritici, the causative agent of stem rust in wheat, is known to rapidly evolve new virulence to resistance genes. While more than 50 stem rust resistance (Sr) loci have been identified in wheat, only a few remain effective, particularly against the highly virulent race Ug99 (TTKSK race) and a mixture of durum-specific races. Association mapping (AM) was deployed on 183 elite durum wheat accessions tested under controlled conditions in order to identify quantitative trait loci (QTLs) for resistance to four highly virulent stem rust races: (TTKSK (Ug99), TRTTF, TTTTF and JRCQC. The panel was genotyped with 1,250 SSR and DArT markers. Overall, 19, 15, 20 and 19 chr. regions harboured markers that were significant for races TTKSK, TRTTF, TTTTF and JRCQC respectively. These genomic regions showed marker R2 values ranging from 1.75 to 23.12, 1.13 to 8.34, 1.92 to 17.64 and 1.51 to 15.33% for races TTKSK, TRTTF, TTTTF and JRCQC respectively. The present study demonstrates that stem rust resistance in durum association panel is governed in part by shared loci and in part by race-specific ones. One QTL on chr. 5A and two QTLs on chr. 6A is common to the resistance for the four races whereas the remaining QTLs are race-specific. Except for race TRTTF, the two QTLs in common on chr. 6A is that with the major effect on the resistance for each race explaining 10.47 to 17.82 and 15.33 to 23.12% for marker barc104 and CD926040 respectively. Combining the results of this study with those on adult plant resistance in the field at Debrezeit where races such as TTKSK, TRTTF and JRCQC are prevalent will provide valuable indications to select suitable parental lines for further improving stem rust resistance of durum wheat. While some markers were linked to known Sr genes (e.g. Sr9, Sr13 and Sr14), other significant markers were located in chr. regions where no Sr genes have been previously reported. The allelic variation identified at these novel QTLs provides additional opportunities to deploy marker-assisted selection to improve adult plant resistance to stem rust in durum wheat.