Abstract

The introgression from wild relatives have a great potential to broaden the availability of beneficial allelic diversity for crop improvement in breeding programs. Here, we assessed the impact of the introgression from 21 diverse accessions of Aegilops tauschii, the diploid ancestor of the wheat D genome, into 6 hard red winter wheat cultivars on yield and yield component traits. We used 5.2 million imputed D genome SNPs identified by the whole-genome sequencing of parental lines and the sequence-based genotyping of introgression population, including 351 BC1F3:5 lines. Phenotyping data collected from the irrigated and non-irrigated field trials revealed that up to 23% of the introgression lines (ILs) produce more grain than the parents and check cultivars. Based on 16 yield stability statistics, the yield of 12 ILs (3.4%) was stable across treatments, years, and locations; 5 of these lines were also high yielding lines, producing 9.8% more grain than the average yield of check cultivars. The most significant SNP- and haplotype-trait associations were identified on chromosome arms 2DS and 6DL for the spikelet number per spike (SNS), on chromosome arms 2DS, 3DS, 5DS, and 7DS for grain length (GL) and on chromosome arms 1DL, 2DS, 6DL, and 7DS for grain width (GW). The introgression of haplotypes from A. tauschii parents was associated with an increase in SNS, which was positively correlated with a heading date (HD), whereas the haplotypes from hexaploid wheat parents were associated with an increase in GW. We show that the haplotypes on 2DS associated with an increase in the spikelet number and HD are linked with multiple introgressed alleles of Ppd-D1 identified by the whole-genome sequencing of A. tauschii parents. Meanwhile, some introgressed haplotypes exhibited significant pleiotropic effects with the direction of effects on the yield component traits being largely consistent with the previously reported trade-offs, there were haplotype combinations associated with the positive trends in yield. The characterized repertoire of the introgressed haplotypes derived from A. tauschii accessions with the combined positive effects on yield and yield component traits in elite germplasm provides a valuable source of alleles for improving the productivity of winter wheat by optimizing the contribution of component traits to yield.

Highlights

  • The gap between population expansion and food production is increasing due to marginal improvements in crop yield, which is attributed to a decline in soil fertility, pests and diseases, and climate change (Bailey-Serres et al, 2019)

  • The effect of treatment on yield was significant in 2018 (p < 2.2e-16), but not in 2019 (p = 0.24) at 95% confidence level. The latter is partially associated with more abundant rainfall in 2019 that reduced the difference in the water availability stress levels between the irrigated and non-irrigated field trials in Colby, KS, USA

  • By the whole-genome sequencing of 6 hexaploid parental lines and 21 A. tauschii accessions used for generating octoploid parents, we identified about 20 million high-quality SNP variants (MAF ≥ 0.05) and used them for genotype imputation in the introgression population genotyped by complexity-reduced sequencing

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Summary

Introduction

The gap between population expansion and food production is increasing due to marginal improvements in crop yield, which is attributed to a decline in soil fertility, pests and diseases, and climate change (Bailey-Serres et al, 2019). The introgression from wild relatives into elite wheat cultivars was reported to increase pest and disease resistance (Periyannan et al, 2013; Saintenac et al, 2013), improve resilience toward environmental stress (Peleg et al, 2005; Placido et al, 2013), and increase yield (Pasquariello et al, 2020). The introgression from Agropyron elongatum into the 7DL chromosome arm of wheat that is known to confer leaf rust resistance (Lr19) (Wang and Zhang, 1996) influences root development, resulting in an improved adaption to water stress (Placido et al, 2013) and salinity (Dvorák et al, 1988), and increased biomass (BM) and yield (Reynolds et al, 2001)

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