Characterization and mapping of stem rust resistance in McNair 701 winter wheat


Saini Sharma, J., Fetch, T., Hiebert, C.W. (2020). Characterization and mapping of stem rust resistance in McNair 701 winter wheat, 42(3), 390-395.

Plain language summary

Stem rust is a highly destructive fungal disease of wheat that can cause catastrophic yield losses. Stem rust can be controlled by developing new varieties of wheat that carry stem rust resistance (Sr) genes that are effective to the population of the stem rust fungus that is present in the region of production. McNair 701 is an old winter wheat variety that has been used in stem rust research for decades. It carries an Sr gene that has not been characterized. As this is an important wheat variety for research, it is important to better understand the Sr gene present in McNair. This was a genetic study that confirmed that McNair carries one Sr gene. Genetic mapping showed that the gene is carried on the wheat chromosome arm 2DL. Further testing suggests that this gene could be the same as a previously identified gene named Sr54.


© 2019 Her Majesty the Queen in Right of Canada, as represented by Agricultural and Agri-Food Canada (AAFC).Wheat stem rust, caused by the fungal pathogen Puccinia graminis f. sp. tritici (Pgt), has re-emerged as an important disease of wheat. This pathogen continues to spread and evolve new virulent races. The international letter-code system of nomenclature has been used to pathotype these new emerging races, and gene SrMcN from ‘McNair 701' winter wheat, which is one of the differential lines, was examined in this study. The chromosome and map position of gene SrMcN have not been determined, and thus the objective of this research was to genetically map SrMcN. A doubled haploid population (n = 186) was made from the cross 'LMPG'/'McNair 701' and inoculated with Pgt race QCCJB. The DH population segregated 95 resistant : 91 susceptible lines, which fitted the expected 1 : 1 ratio (χ2 = 0.09, P = 0.77, NS) for a single gene. SrMcN mapped to chromosome 2DL using the 90K iSelect wheat SNP array, and Kompetitive allele specific (KASP) polymerase chain reaction markers located SrMcN to the same position as Sr54 previously found in ‘Norin 40'. Comparison of stem rust seedling reactions using 12 diverse Pgt races indicated that SrMcN and Sr54 had an identical pattern of responses and similar low infection types (from; to 2−) to races LBBLB, LCBNB and QCCJB. Based on the same chromosomal location on 2DL and identical seedling responses as Sr54 to several races of Pgt with diverse virulence, we assert that the resistance gene in ‘McNair 701' winter wheat previously designated as SrMcN is most likely Sr54.

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