Distribution and Nucleotide Diversity of Yr15 in Wild Emmer Populations and Chinese Wheat Germplasm

Abstract

Stripe rust, caused by Puccinia striiformis f. sp. tritici (Pst), is a devastating fungal disease of wheat. The wild emmer gene, Yr15 (Wtk1), which confers a strong broad-spectrum resistance to Pst isolates, is composed of kinase and pseudokinase domains. The analysis of 361 wild emmer accessions from a wide range of natural habitats confirms that functional Wtk1 is distributed mainly along a narrow axis from Mt. Carmel to Mt. Hermon regions, in the northern part of Israel, where environmental conditions are favorable to the onset of stripe rust. An analysis of full-length Wtk1 DNA sequences from 49 wild emmer accessions identified three haplotypes and extremely low nucleotide diversity (π = 0.00002). The sequence diversity of Wtk1 is 9.5 times lower than that of broad-spectrum partial resistance gene Yr36 (π = 0.00019), and both are in sharp contrast to the high level of nucleotide diversity previously reported for race-specific resistance genes (e.g., Lr10 and Pm3). However, the nonfunctional wtk1 sequences possess high level of nucleotide diversity (π = 0.07). These results may reflect the different resistance mechanisms and the different evolutionary processes that shaped these resistance genes. Yr15 was absent in 189 Chinese wheat landraces and was present in only 1.02% of the 583 tested modern Chinese wheat cultivars. These results corroborate our previous results showing that Yr15 was absent in 94% of a worldwide collection of 513 wheat cultivars, therefore indicating the importance of Yr15 in wheat stripe rust resistance breeding programs in China and elsewhere around the globe.

Development, identification, and utilization of wheat–tetraploid Thinopyrum elongatum 4EL translocation lines resistant to stripe rust

“…To date, many wheat stripe rust resistance genes have been identi ed, some of which were derived from the progenitors or wild relatives of wheat, including Yr5, Yr8, Yr9, Yr15, Yr17, Yr19, Yr28, Yr35, Yr36, Yr37, Yr38, Yr40, Yr42, Yr50, Yr69, Yr70, Yr83, and Yr84 (Gong et al 2022;Klymiuk et al 2022;Li et al 2020). Some of these resistance genes have been widely used by wheat breeders (e.g., Yr5, Yr9, Yr15, Yr17, Yr24, Yr28, and Yr36) (Bariana and Mcintosh 1994;He et al 2020;Zhou et al 2017). Among the 348 wheat germplasm resources analyzed by Dong et al (2019) for the presence of stripe rust resistance genes, 122 were revealed to carry Yr5.…”

Identification of a recessive gene YrZ15-1370 conferring adult plant resistance to stripe rust in wheat-Triticum boeoticum introgression line

“…The highly virulent Pst race CYR34 (virulent on Yr1, Yr6, Yr7, Yr8, Yr9, Yr10, Yr17, Yr18, Yr24, Yr26, Yr27, Yr28, Yr29, Yr31, Yr43, Yr44, YrExp2, and YrSP) (Wang et al 2019b) was used to inoculate the plants at the second leaf stage. Urediniospores used for inoculation of leaf tissue were rst suspended in isododecane and then sprayed as described previously (He et al 2020). Disease severity was evaluated and characterized 14-21 days after inoculation using a 0-9 scale of infection type (IT) (Line and Qayoum 1992).…”