The wheat Sr22, Sr33, Sr35, and Sr45 genes confer resistance against stem rust in barley

Authors: HATTA, M. ASYRAF - JOHN INNES CENTER; ARORA, SANU - JOHN INNES CENTER; GHOSH, SREYA - JOHN INNES CENTER; MATNY, OADI - UNIVERSITY OF MINNESOTA; SMEDLEY, MARK - JOHN INNES CENTER; YU, GUOTAI - JOHN INNES CENTER; CHAKRABORTY, SOMA - COMMONWEALTH SCIENTIFIC AND INDUSTRIAL RESEARCH ORGANISATION (CSIRO); BHATT, DHARA - COMMONWEALTH SCIENTIFIC AND INDUSTRIAL RESEARCH ORGANISATION (CSIRO); XIA, XIAODI - COMMONWEALTH SCIENTIFIC AND INDUSTRIAL RESEARCH ORGANISATION (CSIRO); STEUERNAGEL, BURKHARD - JOHN INNES CENTER; RICHARDSON, TERESE - JOHN INNES CENTER; MAGO, ROHIT - COMMONWEALTH SCIENTIFIC AND INDUSTRIAL RESEARCH ORGANISATION (CSIRO); LAGUDAH, EVANS - COMMONWEALTH SCIENTIFIC AND INDUSTRIAL RESEARCH ORGANISATION (CSIRO); PATRON, NICOLA - EARLHAM INSTITUTE; AYLIFFE, MICHAEL - COMMONWEALTH SCIENTIFIC AND INDUSTRIAL RESEARCH ORGANISATION (CSIRO); ROUSE, MATTHEW; HARWOOD, WENDY - JOHN INNES CENTER; PERIYANNAN, SAMBASIVAM - COMMONWEALTH SCIENTIFIC AND INDUSTRIAL RESEARCH ORGANISATION (CSIRO); STEFFENSON, BRIAN - UNIVERSITY OF MINNESOTA; WULFF, BRANDE - JOHN INNES CENTER

Submitted to: Plant Biotechnology Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/17/2020
Publication Date: 2/1/2021
Citation: Hatta, M.M., Arora, S., Ghosh, S., Matny, O., Smedley, M.A., Yu, G., Chakraborty, S., Bhatt, D., Xia, X., Steuernagel, B., Richardson, T., Mago, R., Lagudah, E.S., Patron, N.J., Ayliffe, M., Rouse, M.N., Harwood, W.A., Periyannan, S., Steffenson, B.J., Wulff, B.B. 2021. The wheat Sr22, Sr33, Sr35, and Sr45 genes confer resistance against stem rust in barley. Plant Biotechnology Journal. 19(2):273-284. https://doi.org/10.1111/pbi.13460.
DOI: https://doi.org/10.1111/pbi.13460

Interpretive Summary: In the last 20 years, stem rust disease has re-emerged as a major threat to wheat and barley production. In contrast to wheat with 60 designated stem rust (Sr) resistance genes, barley only has ten resistance genes identified. Of these, only one complex locus consisting of three genes is effective against the virulent strain of the stem rust fungus known as Ug99. The objective of this study was to assess the functionality, in barley, of cloned wheat Sr genes effective against Ug99. Four wheat Sr genes were transformed into barley. All four genes were found to confer effective stem rust resistance. The barley transgenic plants remained susceptible to the barley leaf rust pathogen, validating the specificity of the resistance conferred by these wheat Sr genes. Furthermore, these transgenic plants did not display significant adverse agronomic effects in the absence of disease. Cloned Sr genes from wheat are therefore a potential source of resistance against wheat stem rust in barley.

Technical Abstract: In the last 20 years, stem rust caused by the fungus Puccinia graminis f. sp. tritici (Pgt), has re-emerged as a major threat to wheat and barley production in Africa and Europe. In contrast to wheat with 60 designated stem rust (Sr) resistance genes, barley’s genetic variation for stem rust resistance is very narrow with only ten resistance genes genetically identified. Of these, only one complex locus consisting of three genes is effective against TTKSK, a widely virulent Pgt race of the Ug99 tribe which emerged in Uganda in 1999 and has since spread to much of East Africa and parts of the Middle East. The objective of this study was to assess the functionality, in barley, of cloned wheat Sr genes effective against race TTKSK. Sr22, Sr33, Sr35 and Sr45 were transformed into barley cv. Golden Promise using Agrobacterium-mediated transformation. All four genes were found to confer effective stem rust resistance. The barley transgenics remained susceptible to the barley leaf rust pathogen Puccinia hordei, indicating that the resistance conferred by these wheat Sr genes was specific for Pgt. Furthermore, these transgenic plants did not display significant adverse agronomic effects in the absence of disease. Cloned Sr genes from wheat are therefore a potential source of resistance against wheat stem rust in barley.