Cloning of the broadly effective wheat leaf rust resistance gene Lr42 transferred from Aegilops tauschii

Authors: LIN, GUIFANG - Kansas State University; CHEN, HUI - Kansas State University; TIAN, BIN - Kansas State University; SEHGAL, SUNISH - South Dakota State University; XIE, JINGZHONG - Kansas State University; JULIAN, PHILOMIN - International Maize & Wheat Improvement Center (CIMMYT); SINGH, NARINDER - Kansas State University; RAWAT, NIDHI - University Of Maryland; SHRESTHA, SANDESK - Kansas State University; WILSON, DUANE - Kansas State University; SHULT, HANNAH - Kansas State University; TIWARI, VIJAY - University Of Maryland; SINGH, RAVI - International Maize & Wheat Improvement Center (CIMMYT); Guttieri, Mary; TRICK, HAROLD - Kansas State University; POLAND, JESSE - Kansas State University; Bowden, Robert; Bai, Guihua; GILL, BIKRAM - Kansas State University; LIU, SANZHEN - Kansas State University

Submitted to: Nature Plants
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/18/2022
Publication Date: 6/1/2022
Citation: Lin, G., Chen, H., Tian, B., Sehgal, S.K., Xie, J., Julian, P., Singh, N., Rawat, N., Shrestha, S., Wilson, D., Shult, H., Tiwari, V.K., Singh, R.P., Guttieri, M.J., Trick, H.N., Poland, J., Bowden, R.L., Bai, G., Gill, B., Liu, S. 2022. Cloning of the broadly effective wheat leaf rust resistance gene Lr42 transferred from Aegilops tauschii. Nature Plants. 13. Article 3044. https://doi.org/10.1038/s41467-022-30784-9.
DOI: https://doi.org/10.1038/s41467-022-30784-9

Interpretive Summary: Wheat varieties resistant to leaf rust are the preferred strategy for managing this economically important disease. Unfortunately, the leaf rust pathogen rapidly overcomes new resistance genes, often within a few years of their use in commercial varieties. One of the ancestral species of wheat, Aegilops tauschii, has been a productive source of new leaf rust resistance genes, among which is Lr42. This research identified several candidate genes for Lr42, then used recombinant DNA technology to insert the most promising of these candidate genes into a leaf rust-susceptible wheat. The resulting transgenic wheat was resistant to the leaf rust pathogen, which confirmed the identity of the resistance gene. Lr42-like sequences were found in wheat and its ancestral species, but the actual Lr42 gene sequence was found only in one Aegilops tauschii. Efficient genetic markers for the Lr42 gene were developed, and these markers will be important tools in the development of resistant wheat varieties that combine Lr42 with other leaf rust resistance genes to prevent the breakdown of the resistance gene(s) by the leaf rust pathogen.

Technical Abstract: The wheat wild relative Aegilops tauschii, a rich resource of genetic variation for wheat improvement, was previously used to transfer the Lr42 resistance gene into bread wheat. Lr42 confers resistance at both seedling and adult plant stages to the leaf rust fungus, Puccinia triticina. It is broadly effective against all leaf rust races tested to date. Lr42 has been used extensively in the CIMMYT international wheat breeding program with resulting cultivars deployed in several countries. Using a bulked segregant RNA-Seq (BSR-Seq) mapping strategy, we identified three candidate genes for Lr42. Transformation of a susceptible wheat line with candidate gene AET1Gv20040300, a nucleotide-binding site leucine-rich repeat (NLR) gene, was sufficient to confer strong resistance to leaf rust. Homologs were found in wheat and wheat relatives, but the Lr42 resistance allele was found only in one accession of Ae. tauschii, suggesting that it is of recent origin. Genetic markers were developed for Lr42 that identified over one thousand CIMMYT wheat breeding lines that carry the Lr42 segment, which significantly enhanced resistance to leaf rust at the seedling stage. Cloning of Lr42 expands the repertoire of cloned rust resistance genes, as well as provides diagnostic DNA markers for wheat improvement. Lr42 should be deployed in combinations with other leaf rust resistance genes to preserve its utility.