Mapping QTLs with additive and epistatic effects for awn length and their effects on kernel-related traits in common wheat

Abstract

Introduction: Wheat awns are crucial determinants of wheat yield due to their capacity to photosynthesize and exchange gas. Understanding the genetic basis of awn length (AL) is essential for improving wheat yield in molecular breeding programs.

Methods: In this study, quantitative trait loci (QTLs) of AL were analyzed using recombinant inbred line (RIL) mapping population referred to as YY-RILs, which was derived from a cross between Yannong 15 (YN15) and Yannong 1212 (YN1212).

Results and discussion: Seven putative additive QTLs and 30 pairwise epistatic QTLs for AL were identified. Among them, five novel additive QTLs (except qAl-2A and qAl-5A.2) and 30 novel pairwise epistatic QTLs were identified. qAl-5A.1 was repeatedly identified in all five environment datasets, which was considered to be one novel stable QTL for AL with minor additive effects. eqAl-2B.2-2 significantly interacted with eight loci and could be of great importance in regulating awn development. The genes associated with the major stable QTL of qAl-5A.2 and the minor stable QTL of qAl-2A were B1 and WFZP-A, respectively. Awn lengths exhibited significant genetic correlations with kernel weight and kernels per spike, which could affect grain protein content to a lesser extent. This study enhances our understanding of the genetic basis of awn development and identifies novel genes as well as markers for future genetic improvement of wheat yield.

Keywords: QTL; awn length; genetic effects; kernel-related traits; wheat.

Figure 1

Morphological differences between Yannong 15 (A) and Yannong 1212 (B) spikes.

Figure 2

Frequency distributions, correlations, and fitting curves of awn length in the YY-RILs under four environments (E1, E2, E3, and E4) and the BLUE dataset. AL, Awn length. E1, E2, E3, and E4 represent Muyu Village of Yantai, Yantai Academy of Agricultural Sciences, Boxing County of Binzhou City, Dryland Farming Institute of Hebei Academy of Agricultural and Forestry Sciences, respectively, during the 2022–2023 period. BLUE represents the best linear unbiased estimator (BLUE) datasets of awn length based on the values obtained from the four environments. *** indicate significance at p < 0.001.

Figure 3

Locations of quantitative trait loci (QTLs) for awn length identified in four environments (E1, E2, E3, and E4) as well as in the best linear unbiased estimator (BLUE) datasets based on the 188 YY-RILs derived from a cross between Yannong 15 and Yannong 112. The short arms of chromosomes are located at the top of the figure. The names of the marker loci and QTLs are listed to the right of the corresponding chromosomes. QTL intervals were based on the logarithm of odds (LOD) scores >2.0, with LOD peak values of more than 2.5 being selected. E1, E2, E3, E4, and BLUE indicate the environments where QTLs were identified. Detailed information is provided in the notes of Figure 1 .

Figure 4

The distribution of logarithm of odds (LOD) values for two stable quantitative trait loci (QTLs), qAl-5A.1 (A) and qAl-5A.2 (B), in four environments as well as in the BLUE datasets. The abscissa represents the genetic position in the linkage map derived from the YY-RILs, and the ordinate indicates the LOD value corresponding to different environment datasets.

Figure 5

Analysis of epistatic quantitative trait loci (QTLs) for awn length. Values on the line represent logarithm of odds (LOD) values of two interacting QTLs, whereas values in the ellipse represent the genetic position (cM) in the genetic linkage map derived from YY-RILs.

Figure 6

Genetic effects of qAl-5A.2 on yield and quality-related traits of wheat grown in four environments (E1, E2, E3, and E4) as well as in the BLUE datasets of the YY-RILs. AL, awn length; KNPS, kernel number per spike; TKW, thousand kernel weight; GPC, grain protein content. * and ** represent significant differences at p < 0.05 and p < 0.01, respectively; NS, not significant. The bar chart in gray and black represent the phenotypic values of the RILs with genotypes identical to Yannong 15 and Yannong 1212, respectively. The detailed phenotypic value information for AL, KNPS, TKW and GPC are shown in (A–D), respectively.