Wild emmer wheat (T. turgidum ssp. dicoccoides, WEW, AABB, 2n = 4x = 28), originated from the Near East Fertile Crescent, is the progenitor of both modern cultivated tetraploid and hexaploid wheat. It harbors many powdery mildew resistance genes that can be used in wheat breeding. Several powdery mildew resistance genes from WEW have been mapped on different chromosomes, but none has been cloned.
Recently, a team led by Prof. LIU Zhiyong at the Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, in collaboration with the team led by Prof. LI Hongjie at the Institute of Crop Sciences, Chinese Academy of Agricultural Sciences, identified a CNL protein in wild emmer wheat that confers resistance to wheat powdery mildew (Blumeria graminis f. sp. tritici).
Using the positional cloning strategy, the powdery mildew resistance gene Pm41 was characterized in WEW accession“IW2”, which encodes a coiled-coil, nucleotide-binding and leucine-rich repeat protein (CNL). Mutagenesis and stable genetic transformation confirmed the CNL is Pm41.
Haplotype analysis of worldwide diversified tetraploid (796) and hexaploid (1122) wheat collections revealed that only 8 WEW accessions (including IW2) carried the Pm41 allele with powdery mildew resistance. None functional alleles of Pm41 with transposon insertions were detected in some accessions of the T. turgidum ssp. dicoccoides, T. turgidum ssp. durum, and common wheat, while the Pm41 genomic region deletion was also found in other accessions of the T. turgidum ssp. dicoccoides, T. turgidum ssp. durum, and common wheat. No homeolog of Pm41 was found in the A and D subgenomes of T. urartu (AA), Aegilops tauschii (DD), T. turgidum ssp. dicoccoides, T. turgidum ssp. durum, and T. aestivum cv. Chinese Spring. However, an ortholog of Pm41 was observed in the chromosome 3H of Hordeum vulgare cultivar Morex.
Pm41 is the first cloning powdery mildew resistance gene from WEW. It was detected with a very low frequency (1.81%) only in the Southern WEW population of Mount Hermon Israel and Bekaa Valley of Lebanon and was absent in the Northern WEW populations, domesticated emmer, durum, and common wheat, suggesting that the ancestral Pm41 was restricted to its place of origin and was not incorporated into domesticated wheat. Pm41 was as highly resistant to Bgt in the hexaploid wheat cultivar Fielder as in the tetraploid WEW accession IW2 following genetic transformation.
Therefore, as a valuable and never exploited powdery mildew resistance gene, Pm41 could make an important contribution to wheat improvement after introgression into cultivated wheat.
The paper entitled “A CNL protein in wild emmer wheat confers powdery mildew resistance” was published in New Phytologist on June 24, 2020 (doi: 10.1111/nph.16761).
This study was supported by the grants from the National Key Research and Development Program of China (2016YFD0101802), National Natural Science Foundation of China (30425039, 31030056) and Science and Technology Service Network Initiative of Chinese Academy of Sciences (KFJ-STS-ZDTP-024).
Contact:
QI Lei
Institute of Genetics and Developmental Biology, Chinese Academy of Sciences
