Abstract
Flowering time is an important trait in wheat breeding as it affects adaptation and yield potential. The aim of this study was to investigate the genetic architecture of flowering time in European winter bread wheat cultivars. To this end a population of 410 winter wheat varieties was evaluated in multi-location field trials and genotyped by a genotyping-by-sequencing approach and candidate gene markers. Our analyses revealed that the photoperiod regulator Ppd-D1 is the major factor affecting flowering time in this germplasm set, explaining 58% of the genotypic variance. Copy number variation at the Ppd-B1 locus was present but explains only 3.2% and thus a comparably small proportion of genotypic variance. By contrast, the plant height loci Rht-B1 and Rht-D1 had no effect on flowering time. The genome-wide scan identified six QTL which each explain only a small proportion of genotypic variance and in addition we identified a number of epistatic QTL, also with small effects. Taken together, our results show that flowering time in European winter bread wheat cultivars is mainly controlled by Ppd-D1 while the fine tuning to local climatic conditions is achieved through Ppd-B1 copy number variation and a larger number of QTL with small effects.
Highlights
Flowering time is one of the most important phenological stages in crop development, as it is key to adaptation, yield potential and yield stability (Snape et al, 2001; Mühleisen et al, 2013)
The aim of this study was to employ a candidate gene approach and genotypingby-sequencing to generate high-density marker data to dissect the genetic architecture of flowering time in European winter bread wheat cultivars
The objectives of our study were to (1) employ high-density genome-wide association mapping to identify main effect QTL for flowering time based on a population of European winter bread wheat with 410 genotypes evaluated in multi-location field trials, (2) assess the frequency of alleles at Ppd, Vrn, and Reduced height (Rht) candidate genes as well as copy number variation at the Ppd-B1 locus and to evaluate their effects on flowering time, (3) assess the contribution of epistasis to the genetic architecture of flowering time, and (4) to draw conclusions for plant breeding
Summary
Flowering time is one of the most important phenological stages in crop development, as it is key to adaptation, yield potential and yield stability (Snape et al, 2001; Mühleisen et al, 2013). Wheat (Triticum aestivum L.) covers more of the world’s surface than any other food crop and has the largest production volume of all staple crops in Europe (FAO, 2013). This worldwide expansion and success were possible because of the adaptability of wheat flowering time to different environmental conditions as facilitated by the vast natural variation provided by the hexaploid wheat genome (Worland and Snape, 2001). For hybrid seed production, the timing of flowering between male and female parental lines has to be synchronized and in addition, the vulnerability during anthesis can result in decreased pollen production (Pickett, 1993; Longin et al, 2013; Langer et al, 2014)
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