Location: Cereal Disease LabTitle: Identification of resistance to races of Puccinia graminis f. sp. tritici with broad virulence in triticale (X Triticosecale)) Author
Submitted to: Plant Disease
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/5/2012
Publication Date: 4/1/2013
Citation: Olivera, P., Pretorius, Z., Babebo, A., Jin, Y. 2013. Identification of resistance to races of Puccinia graminis f. sp. tritici with broad virulence in triticale (X Triticosecale). Plant Disease. 97:479-484. Interpretive Summary: Triticale (X Triticosecale), a hybrid between wheat (Triticum aestivum) and rye (Secale cereale), is known to be an excellent source of resistance to wheat stem rust, a disease caused by the fungus Puccinia graminis f. sp. tritici. However, resistance to the TTKSK (or Ug99) group of races in triticales is unknown. The objective of the study was to identify resistance to Ug99 and other races with broad virulence in triticales deposited at the USDA triticale collection. Based on laboratory and field studies, a high frequency (78.4%) of resistant accessions was found from testing a total of 567 lines. Resistant lines were furhter evaluated against South African stem rust races, enabling us to postulate that a portion of the Ug99 resistance was due to designated stem rust resistance genes known to be present in triticales. A large number of lines (129 total) potentially have novel genes or gene combinations that could be used in wheat breeding. Preliminary genetic studies indicated monogenic resistance in selected resistant lines. Findings from this study will help breeding resistance to Ug99 in wheat using triticale as a source of resistance.
Technical Abstract: Triticale (X Triticosecale), a hybrid between wheat (Triticum aestivum) and rye (Secale cereale), is known to be an excellent source of resistance to wheat stem rust, caused by Puccinia graminis f. sp. tritici. A collection of 567 triticale accessions originating from 21 countries was evaluated for resistance to races of P. graminis f. sp. tritici with broad virulence at the seedling stage, including TTKSK, TRTTF, and TTTTF. A high frequency (78.4%) of accessions was resistant to race TTKSK with low infection types ranging from 0; to X. A selection of 353 TTKSK-resistant accessions were evaluated for their reaction to three South African races of P. graminis f. sp. tritici with virulence, individually or in several combinations, to resistance genes SrSatu, Sr27, and SrKw that are known to be present in triticales. Resistant genes SrSatu, Sr27, and SrKw were postulated to be present in 141 accessions and likely contributed to TTKSK resistance. The remaining 212 resistant accessions may possess uncharacterized genes or combinations of known genes that could not be detected with these races. These accessions were further evaluated for resistance to races TTKST, TPMKC, RKQQC, RCRSC, QTHJC, QCCSM, and MCCFC. Resistance remained effective across the entire set of races in the majority of the accessions (200), suggesting that the resistance is effective against a broad spectrum of virulence. One hundred twenty nine (79.6%) resistant accessions with non-characterized genes were resistant to moderately resistant in field stem rust nurseries at Debre Zeit (Ethiopia) and St. Paul (Minnesota). Results from evaluating F2 populations derived from resistant × susceptible crosses revealed that resistance to TTKSK in triticale was conferred mostly by single genes with dominant effect.