Zhenpu Huang, Jiaqian Liu, Xiangqian Lu, Yifei Guo, Yueying Li, Yangqi Liu, Ruiqi Zhang, Liping Xing & Aizhong Cao

Theoretical and Applied Genetics January 2023; vol. 136: 1–15

Key message

A new functional Pm21 haplotype, Pm21(8#), was cloned from the new wheat-H. villosa translocation line T6VS(8#)·6DL, which confers the same strong resistance to powdery mildew through a different resistance mechanism.

Abstract

Broad-spectrum disease resistance genes are desirable in crop breeding for conferring stable, durable resistance in field production. Pm21(4#) is a gene introduced from wild Haynaldia villosa into wheat that confers broad-spectrum resistance to wheat powdery mildew and has been widely used in wheat production for approximately 30 years. The discovery and transfer of new functional haplotypes of Pm21 into wheat will expand its genetic diversity in production and avoid the breakdown of resistance conferred by a single gene on a large scale. Pm21(4#) previously found from T6VS(4#)·6AL has been cloned. In this study, a new wheat-H. villosa translocation, T6VS(8#)·6DL, was identified. A new functional Pm21 haplotype, designated Pm21(8#), was cloned and characterized. The genomic structures and the splicing patterns of Pm21(4#) and Pm21(8#) were different, and widespread sequence diversity was observed in the gene coding region and the promoter region. In the field, Pm21(8#) conferred resistance to Blumeria graminis f. sp. tritici (Bgt), similar to Pm21(4#), indicating that Pm21(8#) was also a resistance gene. However, Bgt development during the infection stage was obviously different between Pm21(4#)- and Pm21(8#)-containing materials under the microscopic observation. Pm21(4#) inhibited the formation of haustoria and the development of hyphae in the initial infection stage, while Pm21(8#) limited the growth of hyphae and inhibited the formation of conidiophores in the late infection stage. Therefore, Pm21(8#) is a new functional Pm21 haplotype that provides a new gene resource for wheat breeding.

See https://link.springer.com/article/10.1007/s00122-023-04251-y

Fig.1: Cytogenetic identification and molecular marker analysis of the new wheat-H. villosa translocation T6VS(8#)·6DL, a–b Genomic in situ hybridization (GISH) and fluorescence in situ hybridization (FISH) analysis of T6VS(5#)·6DL and T6VS(8#)·6DL on root tip metaphase chromosomes. Green fluorescence represents GISH analysis signal obtained using the total genomic DNA of H. villosa as a probe, and the red fluorescence represents the FISH analysis signal obtained using oligo-pAs as a probe. Chromosomes were counterstained with DAPI (blue). The translocation chromosomes are indicated with white arrows. c–d GISH-FISH patterns of the D-genome chromosomes of the two translocation lines. The chromosomes were extracted from a and b respectively, and the two translocation chromosomes, 6VS(5#)·6DL and 6VS(8#)·6DL, were identified and are indicated. e PCR analysis of the codominant molecular marker CINAU15. The chromosome specific bands are labeled on the right, and the band of 6VS(8#) was different from that of 6VS(4#) or 6VS(5#) (color figure online).