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.
Bibliographical noteFunding Information:
Funding: This work was financially supported by the National Natural Science Foundation of China (No. 31801360; No. 31901493; No. 31671689), the Science & Technology Department of Sichuan Province (No. 2019YJ0435), the Education Department of Sichuan Province (No. 18ZA0392), the Sichuan International Science and Technology Cooperation and Exchange Research and Development Project (2018HH0116), the Israel Science Foundation (1366/18), and the China–Israel cooperation program grant from the Ministry of Science and Technology in China (2013DFA32200).
© 2020 by the authors. Licensee MDPI, Basel, Switzerland.
- Chinese wheat germplasm
- Nucleotide diversity
- Stripe rust resistance
- Wild emmer populations
ASJC Scopus subject areas
- Immunology and Allergy
- Molecular Biology
- Immunology and Microbiology (all)
- Microbiology (medical)
- Infectious Diseases