|ZHANG, WENJUN - University Of California|
|CHEN, SHISHENG - University Of California|
|ABATE, ZEWDIE - University Of California|
|NIRMALA, JAYAVEERAMUTHU - University Of Minnesota|
|Rouse, Matthew - Matt|
|DUBCOVSKY, JORGE - University Of California|
Submitted to: Proceedings of the National Academy of Sciences (PNAS)
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/25/2017
Publication Date: 10/23/2017
Citation: Zhang, W., Chen, S., Abate, Z., Nirmala, J., Rouse, M.N., Dubcovsky, J. 2017. Identification and characterization of Sr13, a tetraploid wheat gene that confers resistance to the Ug99 stem rust race group. Proceedings of the National Academy of Sciences. http://www.pnas.org/cgi/doi/10.1073/pnas.1706277114.
Interpretive Summary: Wheat provides a substantial proportion of the calories and proteins consumed by the human population but further increases in wheat production are necessary to feed a growing human population. Reducing yield losses caused by pathogens can contribute to these increases. In this study, we report the identification of Sr13, a gene from pasta wheat that confers resistance to the new virulent races of the stem rust pathogen that appeared in Africa at the beginning of this century. We identified three different resistance forms of Sr13 and developed perfect markers to accelerate their deployment in wheat breeding programs. In addition, this gene can be a useful component of transgenic cassettes including multiple resistance genes.
Technical Abstract: The Puccinia graminis f. sp. tritici (Pgt) Ug99 race group is virulent to most stem rust resistance genes currently deployed in wheat and poses a serious threat to global wheat production. The durum wheat (Triticum turgidum ssp. durum) gene Sr13 confers resistance to Ug99 in addition to virulent races TKTTF and TRTTF. Using map-based cloning, we delimited a candidate region including two linked genes encoding coiled-coil nucleotide-binding leucine-rich repeat proteins designated CNL3 and CNL13. Three independent truncation mutations identified in each of these genes demonstrated that only CNL13 was required for Ug99-resistance. Transformation of an 8-kb genomic sequence including CNL13 into the susceptible wheat variety Fielder was sufficient to confer resistance to Ug99, confirming that CNL13 is Sr13. CNL13 transcripts were slightly down-regulated 2-6 days after Pgt inoculation and were not affected by temperature. CNL13:GFP and GFP:CNL13 fusion proteins were localized in the cytoplasm of rice protoplasts. We identified three Sr13 resistant haplotypes, present in 31% of T. turgidum ssp. dicoccon and 37% of cultivated pasta wheats, but absent in most tested common wheats (T. aestivum). These results suggest that Sr13 is effective to virulent Pgt races and can improve Ug99-resistance in a large proportion of modern pasta and bread wheat cultivars. To accelerate the deployment of Sr13, we developed a diagnostic marker based on a T2200C polymorphism that differentiates all known susceptible and resistant haplotypes. The identification of Sr13 also expands the number of Pgt-resistance genes that can be incorporated into multi-gene transgenic cassettes to control this devastating disease.