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. 2023 Feb 23:14:1131205.
doi: 10.3389/fpls.2023.1131205. eCollection 2023.

Physical mapping of a new powdery mildew resistance locus from Thinopyrum ponticum chromosome 4AgS

Guotang Yang  1   2 , Pingchuan Deng  3 , Wanquan Ji  3 , Shulan Fu  4 , Hongwei Li  1 , Bin Li  1 , Zhensheng Li  1 , Qi Zheng  1
Affiliations

Physical mapping of a new powdery mildew resistance locus from Thinopyrum ponticum chromosome 4AgS

Guotang Yang et al. Front Plant Sci. .

Abstract

Thinopyrum ponticum (Podp.) Barkworth and D.R. Dewey is a decaploid species that has served as an important genetic resource for improving wheat for the better part of a century. The wheat-Th. ponticum 4Ag (4D) disomic substitution line Blue 58, which was obtained following the distant hybridization between Th. ponticum and common wheat, has been stably resistant to powdery mildew under field conditions for more than 40 years. The transfer of 4Ag into the susceptible wheat cultivar Xiaoyan 81 resulted in powdery mildew resistance, indicating the alien chromosome includes the resistance locus. Irradiated Blue 58 pollen were used for the pollination of the recurrent parent Xiaoyan 81, which led to the development of four stable wheat-Th. ponticum 4Ag translocation lines with diverse alien chromosomal segments. The assessment of powdery mildew resistance showed that translocation line L1 was susceptible, but the other three translocation lines (WTT139, WTT146, and WTT323) were highly resistant. The alignment of 81 specific-locus amplified fragments to the Th. elongatum genome revealed that 4Ag originated from a group 4 chromosome. The corresponding physical positions of every 4Ag-derived fragment were determined according to a cytogenetic analysis, the amplification of specific markers, and a sequence alignment. Considering the results of the evaluation of disease resistance, the Pm locus was mapped to the 3.79-97.12 Mb region of the short arm of chromosome 4Ag. Because of its durability, this newly identified Pm locus from a group 4 chromosome of Th. ponticum may be important for breeding wheat varieties with broad-spectrum disease resistance.

Keywords: 4Ag; Pm gene; Thinopyrum ponticum; cytogenetic analysis; physical mapping; specific marker amplification.

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Conflict of interest statement

The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

Figures

Figure 1
Figure 1
Procedure for producing wheat–Th. ponticum 4Ag translocation lines.
Figure 2
Figure 2
The powdery mildew resistance evaluation and cytogenetic analysis. (A) The powdery mildew resistance evaluation at the adult plant stage. (B) The powdery mildew resistance evaluation at the seedling stage. (C) The GISH pattern of 19ZQ43 probed with total genomic DNA of Th. ponticum. (D) The mc-FISH pattern of 19ZQ43 using probes pAs1 (red) and pSc119.2 (green). 1: Blue 58; 2: Xiaoyan 81; 3: 19ZQ43. The arrows note a pair of 4Ag chromosomes. Bar = 20 μm.
Figure 3
Figure 3
Phenotypic images of Xiaoyan 81 and four wheat–Th. ponticum 4Ag translocation lines.
Figure 4
Figure 4
Sequential GISH and mc-FISH analysis of translocation lines. (A) The GISH pattern of L1 with total genomic DNA of Th. ponticum as a probe. (B) The mc-FISH pattern of L1 using two probes pAs1 (red) and pSc119.2 (green). (C) The GISH pattern of WTT139. (D) The mc-FISH pattern of WTT139. (E) The GISH pattern of WTT146. (F) The mc-FISH pattern of WTT146. (G) The GISH pattern of WTT323. (H) The mc-FISH pattern of WTT323. The arrows note a pair of translocated chromosomes. Bar = 20 μm.
Figure 5
Figure 5
The powdery mildew resistance responses of four translocation lines and Xiaoyan 81.
Figure 6
Figure 6
Alignment results of 81 specific SLAFs to Th. elongatum genome using Bowtie 2.
Figure 7
Figure 7
Synteny analysis and PCR amplification. (A) Synteny relationship of specific marker amplification products between Th. elongatum chromosome 4E and Th. ponticum chromosome LG34. (B) Amplified results in Blue 58, four translocation lines and Xiaoyan 81. The symbols ‘+’ and ‘−’ indicate the presence and absence of the specific marker loci, respectively. The dotted box indicates the physical region of Pm locus.
Figure 8
Figure 8
Amplified results of three specific markers of WTT146. M: Marker II; 1: Blue 58; 2: WTT146; 3: J146; 4: Jimai 22.
See this image and copyright information in PMC

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