QTL-seq identifies BnaFT.A02 and BnaFLC.A02 as candidates for variation in vernalization requirement and response in winter oilseed rape (Brassica napus).

Eleri H Tudor,Ian Bancroft,Judith A Irwin,Caroline Dean,Rachel Wells,D Marc Jones,Zhesi He,Martin Trick

doi:10.1111/pbi.13421

Eleri H Tudor, Ian Bancroft + Show 6 more

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https://doi.org/10.1111/pbi.13421

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Abstract

SummaryWinter, spring and biennial varieties of Brassica napus that vary in vernalization requirement are grown for vegetable and oil production. Here, we show that the obligate or facultative nature of the vernalization requirement in European winter oilseed rape is determined by allelic variation at a 10 Mbp region on chromosome A02. This region includes orthologues of the key floral regulators FLOWERING LOCUS C (BnaFLC.A02) and FLOWERING LOCUS T (BnaFT.A02). Polymorphism at BnaFLC.A02 and BnaFT.A02, mostly in cis‐regulatory regions, results in distinct gene expression dynamics in response to vernalization treatment. Our data suggest allelic variation at BnaFT.A02 is associated with flowering time in the absence of vernalization, while variation at BnaFLC.A02 is associated with flowering time under vernalizing conditions. We hypothesize selection for BnaFLC.A02 and BnaFT.A02 gene expression variation has facilitated the generation of European winter oilseed rape varieties that are adapted to different winter climates. This knowledge will allow for the selection of alleles of flowering time regulators that alter the vernalization requirement of oilseed rape, informing the generation of new varieties with adapted flowering times and improved yields.

Highlights

Vernalization leads to an acceleration of flowering in response to cold temperatures
Mutations at AtFRI that disrupt protein function result in a loss of vernalization requirement (Johanson et al, 2000; Michaels et al, 2004; Shindo et al, 2005), while allelic variation at AtFLC is important for fine-tuning the vernalization response (Agren et al, 2013; Coustham et al, 2012; Duncan et al, 2015; Grillo et al, 2013; Li et al, 2014; Li et al, 2015; Shindo et al, 2006; Strange et al, 2011)
Under vernalization treatment at °C (VERN), Cabriolet flowered within an average of 42.92 days after transfer to the poly-tunnel, while Darmor flowered within an average of 71.25 days (141.25 days after sowing) and exhibited a broader range of flowering times, indicative of incomplete vernalization (Table S1)

Summary

Introduction

Vernalization leads to an acceleration of flowering in response to cold temperatures. Manipulation of the requirement for, and responsiveness to, vernalization has facilitated the generation of novel crop varieties that are adapted to local environments (Jung and Muller, 2009). In seed crops, such as oilseed rape (Brassica napus, 2n = 4x = 38, AACC), predictable and synchronized flowering is essential for a harvestable product. In A. thaliana, allelic variation at two loci, FRIGIDA (AtFRI) and FLOWERING LOCUS C (AtFLC), often underlies variation in reproductive strategy (Shindo et al, 2005; Stinchcombe et al, 2004). Mutations at AtFRI that disrupt protein function result in a loss of vernalization requirement (Johanson et al, 2000; Michaels et al, 2004; Shindo et al, 2005), while allelic variation at AtFLC is important for fine-tuning the vernalization response (Agren et al, 2013; Coustham et al, 2012; Duncan et al, 2015; Grillo et al, 2013; Li et al, 2014; Li et al, 2015; Shindo et al, 2006; Strange et al, 2011)

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