Abstract

Wheat breeders select for qualitative and quantitative traits, the latter often detected as quantitative trait loci (QTL). It is, however, a long procedure from QTL discovery to the successful introduction of favourable alleles into new elite varieties and finally into farmers’ crops. As a proof of principle for this process, QTL for grain yield (GY), yield components, plant height (PH), ear emergence (EM), solid stem (SS) and yellow rust resistance (Yr) were identified in segregating UK bread wheat reference population, Avalon × Cadenza. Among the 163 detected QTL were several not reported before: 17 for GY, the major GY QTL on 2D; a major SS QTL on 3B; and Yr6 on 7B. Common QTL were identified on ten chromosomes, most interestingly, grain number (GN) was found to be associated with Rht-D1b; and GY and GN with a potential new allele of Rht8. The interaction of other QTL with GY and yield components was discussed in the context of designing a UK breeding target genotype. Desirable characteristics would be: similar PH and EM to Avalon; Rht-D1b and Vrn-A1b alleles; high TGW and GN; long and wide grains; a large root system, resistance to diseases; and maximum GY. The potential of the identified QTL maximising transgressive segregation to produce a high-yielding and resilient genotype was demonstrated by simulation. Moreover, simulating breeding strategies with F2 enrichment revealed that the F2–DH procedure was superior to the RIL and the modified SSD procedure to achieve that genotype. The proposed strategies of parent selection and breeding methodology can be used as guidance for marker-assisted wheat breeding.Electronic supplementary materialThe online version of this article (doi:10.1007/s11032-015-0268-7) contains supplementary material, which is available to authorized users.

Highlights

  • Wheat breeders select simultaneously for qualitative traits controlled by one or a small number of major genes and quantitative traits controlled by multiple genes which may be detected as quantitative trait loci (QTL)

  • Our objectives were (1) to use a high-density map to identify QTL for grain yield (GY), grain number (GN), solid stem (SS) and yellow rust resistance (Yr) gene Yr6, and to remap thousand grain weight (TGW), grain width (GRW), grain length (GRL), plant height (PH) and EM QTL by multi-environment analysis and re-identify Yr7; (2) to study trade-offs between GY with other traits; (3) to predict the performance of GY, PH and EM for some perfect genotypes generated by simulation under different environments; (4) to design a superior genotype comprising all or if not most favourable alleles based on QTL identified here and published QTL and genes, and to compare the efficiency of three breeding procedures involving Markerassisted selection (MAS) in terms of genetic gain and number of target lines retained from one breeding cycle through simulation

  • A total of 163 QTL were identified in the Avalon 9 Cadenza population mainly by multi-environment QTL analysis; among them, 17 QTL were for GY, 47 QTL for yield component traits, 53 QTL for PH, 33 QTL for EM, five QTL for SS and eight QTL for Yr

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Summary

Introduction

Wheat breeders select simultaneously for qualitative traits controlled by one or a small number of major genes and quantitative traits controlled by multiple genes which may be detected as quantitative trait loci (QTL). There are many complex choices to be made, from the selection of the best parents for a cross through to selection strategies that result in combining multiple desired alleles into a single target genotype, all at minimum cost to the breeding programme. It is a lengthy procedure from gene discovery to superior varieties in farmers’ fields. Grain yield (GY) improvement is the main objective in wheat breeding programmes. The Avalon 9 Cadenza segregating population represents a broad spectrum of elite UK winter germplasm produced in different UK wheat breeding programmes. The population has been widely used to assess multiple traits via QTL analysis such as: grain size and shape (Gegas et al 2010), plant

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