Characterization of synthetic wheat line Largo for resistance to stem rust

Authors: SHARMA, JYOTI - North Dakota State University; Overlander-Chen, Megan; Faris, Justin; Klindworth, Daryl; Rouse, Matthew; KANG, HOUYANG - North Dakota State University; LONG, YUNMING - North Dakota State University; Jin, Yue; LAGUDAH, EVANS - Csiro, Black Mountain Laboratories; Xu, Steven

Submitted to: Genes, Genomes, Genetics
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/17/2021
Publication Date: 6/4/2021
Citation: Sharma, J.S., Overlander, M., Faris, J.D., Klindworth, D.L., Rouse, M.N., Kang, H., Long, Y., Jin, Y., Lagudah, E.S., Xu, S.S. 2021. Characterization of synthetic wheat line Largo for resistance to stem rust. Genes, Genomes, Genetics. https://doi.org/10.1093/g3journal/jkab193.
DOI: https://doi.org/10.1093/g3journal/jkab193

Interpretive Summary: Bread wheat originated from natural hybridizations involving three grass relatives. These hybridizations can be reconstructed under controlled conditions to ‘re-create’ bread wheat and produce what is called synthetic wheat. Synthetic wheat lines can be used as bridges to introduce useful genes from the grass relatives into modern wheat lines. The synthetic wheat line Largo, which was previously discovered to have resistance to the wheat insect pest known as greenbug, was recently found to have resistance to the fungal pathogen that causes the disease stem rust. We conducted genetic analysis of Largo and found that it contains five different stem rust resistance genes. Another wheat line used in the study was found to contain a stem rust resistance gene as well. Among these genes, four were previously identified in other wheat lines and two were new. Knowledge of the stem rust resistance genes in Largo will help wheat breeders to design breeding experiments aimed at the development of new stem rust-resistant wheat germplasm and varieties.

Technical Abstract: Resistance breeding is an effective approach against wheat (Triticum aestivum L.) stem rust caused by Puccinia graminis f. sp. tritici (Pgt). The synthetic hexaploid wheat line Largo (pedigree: durum wheat ‘Langdon’ × Aegilops tauschii PI 268210) was found to have resistance to a broad spectrum of Pgt races including the Ug99 race group. To identify and characterize the stem rust resistance (Sr) genes in Largo, we genotyped a population of 188 recombinant inbred lines developed from a cross between the susceptible wheat line ND495 and Largo using the 90K wheat chip, and we evaluated the population for reaction to the Pgt races TTKSK, TRTTF, and TTTTF. Based on genetic linkage analysis using the marker and rust data, we identified six QTL with effectiveness against different races. Three QTL on chromosome arms 6AL, 2BL, and 2BS corresponded to Sr genes Sr13c, Sr9e, and a likely new Sr gene derived from Langdon, respectively. Two other QTL derived from PI 268210 on 2DS and 1DS were associated with a potentially new allele of Sr46 and a likely new Sr gene, respectively. Additionally, Sr7a was identified as the underlying gene for the 4AL QTL derived from ND495. Knowledge of the Sr genes present in Largo will help to design breeding experiments aimed at the development of new stem rust-resistant wheat germplasm and varieties. Largo and its derived lines developed are particularly useful for simultaneously introducing two Ug99-effective genes Sr13c and Sr46 into modern bread wheat varieties for controlling Ug99 and other emerging Pgt races.