The potential of pale flax as a source of useful genetic variation for cultivated flax revealed through molecular diversity and association analyses.

Braulio J Soto-Cerda,Axel Diederichsen,Helen Booker,Scott Duguid,Gordon Rowland,Sylvie Cloutier

doi:10.1007/s11032-014-0165-5

Abstract

Pale flax (Linum bienne Mill.) is the wild progenitor of cultivated flax (Linum usitatissimum L.) and represents the primary gene pool to broaden its genetic base. Here, a collection of 125 pale flax accessions and the Canadian flax core collection of 407 accessions were genotyped using 112 genome-wide simple sequence repeat markers and phenotyped for nine traits with the aim of conducting population structure, molecular diversity and association mapping analyses. The combined population structure analysis identified two well-supported major groups corresponding to pale and cultivated flax. The L. usitatissimum convar. crepitans accessions most closely resembled its wild progenitor, both having dehiscent capsules. The unbiased Nei’s genetic distance (0.65) confirmed the strong genetic differentiation between cultivated and pale flax. Similar levels of genetic diversity were observed in both species, albeit 430 (48 %) of pale flax alleles were unique, in agreement with their high genetic differentiation. Significant associations were identified for seven and four traits in pale and cultivated flax, respectively. Favorable alleles with potentially positive effect to improve yield through yield components were identified in pale flax. The allelic frequencies of markers associated with domestication-related traits such as capsular dehiscence indicated directional selection with the most common alleles in pale flax being absent or rare in cultivated flax and vice versa. Our results demonstrated that pale flax is a potential source of novel variation to improve multiple traits in cultivated flax and that association mapping is a suitable approach to screening pale flax germplasm to identify favorable quantitative trait locus alleles.Electronic supplementary materialThe online version of this article (doi:10.1007/s11032-014-0165-5) contains supplementary material, which is available to authorized users.

Highlights

Plant breeders select favorable alleles to introduce new variation (Sim et al 2011)
The Bayesian-based clustering approach implemented in STRUCTURE identified two major groups according to the Dk approach (Fig. 1a, Online Resource 2), which corresponded to the pale and cultivated flax accessions
The genetic diversity in cultivated flax, one of the oldest oil and fiber crop domesticated by early civilizations, has been generally described as narrow (Cloutier et al 2009; Diederichsen and Fu 2006; Fu et al 2002, 2003; Smykal et al 2011; Soto-Cerda et al 2012)

Summary

Introduction

Plant breeders select favorable alleles to introduce new variation (Sim et al 2011). as the genetic base of breeding populations narrows through selection and fixation of specific alleles, breeding progress is hampered (Sim et al 2011). On the other hand, cultivated flax is mostly a spring annual plant that has variable seed dormancy, grows fast, flowers early, with almost indehiscent capsules and large seeds (Diederichsen and Richards 2003). Because both species share the same chromosome number (n = 15) and produce fully fertile offspring, pale flax represents cultivated flax’s primary gene pool (Diederichsen 2007), which can be accessed to broaden its generally narrow genetic bases (Cloutier et al 2009; Diederichsen and Fu 2006; Fu et al 2002, 2003; Smykal et al 2011; Soto-Cerda et al 2012).

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Conclusion