Abstract
Key messageQuantitative trait locus (QTL) mapping of 15 yield component traits in a German multi-founder population identified eight QTL each controlling ≥2 phenotypes, including the genetic loci Rht24, WAPO-A1 and WAPO-B1.Grain yield in wheat (Triticum aestivum L.) is a polygenic trait representing the culmination of many developmental processes and their interactions with the environment. Toward maintaining genetic gains in yield potential, ‘reductionist approaches’ are commonly undertaken by which the genetic control of yield components, that collectively determine yield, are established. Here we use an eight-founder German multi-parental wheat population to investigate the genetic control and phenotypic trade-offs between 15 yield components. Increased grains per ear was significantly positively correlated with the number of fertile spikelets per ear and negatively correlated with the number of infertile spikelets. However, as increased grain number and fertile spikelet number per ear were significantly negatively correlated with thousand grain weight, sink strength limitations were evident. Genetic mapping identified 34 replicated quantitative trait loci (QTL) at two or more test environments, of which 24 resolved into eight loci each controlling two or more traits—termed here ‘multi-trait QTL’ (MT-QTL). These included MT-QTL associated with previously cloned genes controlling semi-dwarf plant stature, and with the genetic locus Reduced height 24 (Rht24) that further modulates plant height. Additionally, MT-QTL controlling spikelet number traits were located to chromosome 7A encompassing the gene WHEAT ORTHOLOG OF APO1 (WAPO-A1), and to its homoeologous location on chromosome 7B containing WAPO-B1. The genetic loci identified in this study, particularly those that potentially control multiple yield components, provide future opportunities for the targeted investigation of their underlying genes, gene networks and phenotypic trade-offs, in order to underpin further genetic gains in yield.
Highlights
Bread wheat (Triticum aestivum L.) is one of the world’s most widely cultivated crops, accounting for more than 20% of human calorific intake (FAO 2017)
All Bavarian MAGIC winter wheat population (BMWpop) recombinant inbred lines (RILs) carried haplotypes000′ or222′, except for two lines carrying haplotype ‘002′ which were excluded for the purposes of the analysis presented here. (g) WAPO-A1, -B1 and -D1 gene expression in the apical meristem at different stages of development, measured as transcripts per million reads (TPM), sourced from Li et al (2018b)
We found Reduced height 24 (Rht24) to be the second most important of the three ‘plant height’ quantitative trait loci (QTL) identified after Reduced height (Rht)-D1, in agreement with previous analysis in the BMWpop (Stadlmeier et al 2019)
Summary
Bread wheat (Triticum aestivum L.) is one of the world’s most widely cultivated crops, accounting for more than 20% of human calorific intake (FAO 2017). While exceptions do exist, most notably a locus on chromosome 7A controlling spikelet number per ear (Muqaddasi et al 2019; Kuzay et al 2019; Voss-Fels et al 2019), natural variation at wheat genetic loci controlling yield and yield component traits in bread wheat typically control just ~ 2–10% of the variation (reviewed by Brinton and Uauy, 2019) This observation is likely due to the compensatory effects of homoeologous genes in polyploid wheat. It encodes an F-box protein orthologous to the rice gene ABBERANT PANICLE ORGANISATION 1 (APO1) which controls rice spikelet number (Ikeda et al 2007), and is homologous to UNUSUAL FLORAL ORGANS (UFO) that regulates arabidopsis floral organ identity (Wilkinson et al 1995; Samach et al 1999)
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