|Rouse, Matthew - Matt|
|ACEVEDO, MARICELIS - North Dakota State University|
|SZABO-HEVER, AGNES - North Dakota State University|
|ELIAS, ELIAS - North Dakota State University|
Submitted to: The Plant Genome
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/5/2016
Publication Date: 7/13/2017
Publication URL: https://handle.nal.usda.gov/10113/6471044
Citation: Chao, S., Rouse, M.N., Acevedo, M., Szabo-Hever, A., Bockelman, H.E., Bonman, J.M., Elias, E., Klindworth, D.L., Xu, S.S. 2017. Evaluation of genetic diversity and host resistance to stem rust in USDA NSGC durum wheat accessions. The Plant Genome. 10(2). 10.3835/plantgenome2016.07.0071.
Interpretive Summary: Wheat stem rust caused by a fungal pathogen poses a significant threat to wheat production throughout the world. In particular, the recently emerged race from East Africa known as Ug99 and its variants have impacted over 90% of the wheat cultivars grown worldwide. The USDA-ARS National Small Grains Collection (NSGC) located in Aberdeen, ID, maintains collections representing the global diversity of small grains and their wild relatives. In this study, we evaluated a set of 429 NSGC durum wheat samples originating from 64 countries worldwide for resistance to stem rust pathogens in the greenhouse and in the field, and identified samples resistant to the pathogens evaluated. The resistant samples identified in this study should provide wheat breeders with valuable resources for improving stem rust resistance to combat this devastating disease.
Technical Abstract: The USDA-ARS National Small Grains Collection (NSGC) located in Aberdeen, ID, maintains collections representing the global diversity of small grains and their wild relatives. To evaluate the utility of the NSGC durum wheat accessions, we assessed genetic diversity and LD patterns in a durum core subset containing 429 lines with spring growth habit originating from 64 countries worldwide. Genetic diversity estimated using wheat SNP markers showed a considerable amount of diversity captured in this collection. Population structure was generally weak with an overall Fst value of 0.06. Average LD decayed over a genetic distance to within 3 cM at r2 = 0.2, with a fast LD decay for markers linked at > 5 cM. We then evaluated the accessions for resistance to wheat stem rust using races TTKSK (Ug99), TRTTF, JRCQC, and a bulk of six North American races at the seedling and adult plant stages. Five accessions were identified as resistant to all stem rust pathogen races evaluated. Genome-wide association analysis detected 17 significant associations at the seedling stage with nine likely corresponding to Sr7, Sr12, and Sr13, and the remaining potentially being novel genes located on six chromosomes. A higher frequency of resistant accessions was found at the adult plant stage than at the seedling stage. However, few significant associations were detected possibly due to strong G × E interactions not properly accounted for in the mixed model. Nonetheless, the resistant accessions identified in this study should provide wheat breeders with valuable resources for improving stem rust resistance.