Identification of a locus on Agropyron cristatum chromosome 6P that interacts with wheat genes to produce yellow-green leaves

Abstract

Background: Wide hybridization is crucial for broadening the genetic basis of common wheat. Agropyron cristatum (2n = 4x = 28, PPPP), a wild relative of wheat, harbors numerous favorable genes for genetic improvement. The variability related to the expression of alien genes in different wheat backgrounds is a crucial factor that limits the effective utilization of these genes.

Results: In this study, the introduction of chromosome 6P from A. cristatum into different wheat backgrounds resulted in different leaf colors: green in plants with the Fukuho background and yellow‒green in plants with the Jimai 22 background. Genetic analysis suggested that yellow‒green leaves were caused by gene interactions between chromosome 6P and genes from the Jimai 22 background, which negatively affected agronomic traits. To determine the locus on chromosome 6P responsible for yellow‒green leaves, six wheat-A. cristatum deletion lines and five wheat-A. cristatum translocation lines were crossed with Jimai 22 to produce F₁ progeny for leaf color investigation. We found that the F₁ progeny carrying the short arm of chromosome 6P (6PS) presented yellow-green leaves, and the relevant locus was ultimately mapped to 6PS (0.81-1.00). A total of 50 A. cristatum genes related to chlorophyll catabolite reductase and chloroplast development were annotated within this interval.

Conclusions: A locus on chromosome 6P of A. cristatum that caused a yellow-green leaf in the Jimai 22 background was mapped to chromosome 6PS (0.81-1.00). This study provides valuable germplasm for the study of leaf color and guidance for the use of valuable genes on A. cristatum chromosome 6P.

Keywords: Agropyron cristatum; Chromosome 6P; Common wheat; Translocation line; Yellow–green leaf gene.

Fig. 1

Leaf color of the 4844-12 F₁ progeny in the Fukuho and Jimai 22 backgrounds. (a) Plant color. (b) Leaf color. 4844-12, wheat–A. cristatum 6P disomic addition line; Fu, common wheat Fukuho; Jimai 22, common wheat Jimai 22; F₁(Fu), F₁ plant from the cross of 4844-12 and Fukuho; F₁(Jimai 22), F₁ plant from the cross of 4844-12 and Jimai 22. The bars in (a) and (b) represent 10.0 cm and 1.0 cm, respectively

Fig. 2

Molecular marker identification and leaf color observation of the 4844-12/Jimai 22 F₂ progeny. (a) Identification of F₂ progeny via the molecular markers Agc71415 and Agc10030. M, DL2000; 1, A. cristatum Z559; 2, wheat–A. cristatum 6P disomic addition line 4844-12; 3, common wheat Jimai 22; 4–12, the F₂ progeny of 4844-12 and Jimai 22. The arrows indicate the diagnostic bands. (b) Leaf color of 4844-12 F₂ progeny in the Fukuho background. (c) Leaf color of 4844-12 F₂ progeny in the Jimai 22 background. In (b) and (c), ‘+’ indicates that the materials can be detected by A. cristatum-specific markers; ‘−’ indicates that the materials cannot be detected by A. cristatum-specific markers. The plants with two ‘+’ signs are those carrying chromosome 6P in the population. Plants with two ‘−’ signs are those not carrying chromosome 6P in the population

Fig. 3

Agronomic traits of yellow–green leaf progeny in the 4844-12 population. ‘green (6P+)’ indicates that the materials can be detected by A. cristatum-specific markers and have a green leaf color; ‘yellow‒green (6P+)’ indicates that the materials can be detected by A. cristatum-specific markers and have a yellow‒green leaf color. (a–f) Comparisons of agronomic traits, including plant height (a), fertile tillers (b), spike length (c), kernel number per spikelet (d), grain number per spike (e), and thousand-grain weight (f)

Fig. 4

Cytogenetic identification and leaf color observation of F₁-positive progeny derived from Jimai 22 with chromosomes 6PS and 6PL. (a-d) GISH patterns of wheat–A. cristatum 6PS telosomic line del10b, 6PL telosomic line del18, T6PS·6DL translocation line L934-5, and T6DS·6PL translation line L933-11 in the Jimai 22 background; the insets in (a, b, c, d) show higher magnification images of the A. cristatum chromosome 6P segments. (e) Schematic diagram of telosomic and translocation lines del18, del10b, L934-5, and L933-11. (f) Leaf color of Fukuho and Jimai 22 with del10b and del18. 1–8 in (f) represent del10b, del18, Fukuho, Jimai 22, the F₁ plant of del10b with Fukuho, the F₁ plant of del10b with Jimai 22, the F₁ plant of del18 with Fukuho, and the F₁ plant of del18 with Jimai 22, respectively. (g) Leaf color of Fukuho and Jimai 22 with L934-5 and L933-11. 1–8 in (g) represent L934-5, L933-11, Fukuho, Jimai 22, the F₁ plant of L934-5 with Fukuho, the F₁ plant of L934-5 with Jimai 22, the F₁ plant of L933-11 with Fukuho, and the F₁ plant of L933-11 with Jimai 22, respectively. The bars in (f) and (g) represent 1.0 cm

Fig. 5

Leaf color of F₁ progeny derived from Jimai 22 with different chromosome 6P deletion or translocation lines. (a) F₁ leaf color of Jimai 22 with different wheat–A. cristatum 6P deletion and translocation lines. (b) Chromosome location of the yellow–green leaf locus on A. cristatum chromosome 6P

Fig. 6

Development of specific markers for A. cristatum genes and expression validation in plants with yellow–green and green leaves. (a) Specific markers for the A. cristatum genes Ac6P01G034600.1 and Ac6P01G047400.1. M, DL2000; 1, F₂ plants of 4844-12 and Jimai22 with a green leaf color; 2, F₂ plants of 4844-12 and Jimai22 with a yellow–green leaf color; 3, common wheat Jimai 22. (b) Verification of the expression levels of the A. cristatum genes in plants with yellow–green and green leaves