Population genetic structure in Fennoscandian landrace rye (Secale cereale L.) spanning 350\xa0years

P Larsson,M Lundström,P Lagerås,H R Oliveira,M W Leino,J Hagenblad

doi:10.1007/s10722-019-00770-0

Abstract

Rye (Secale cereale L.) was for centuries the economically most important crop in Fennoscandia (Denmark, Finland, Norway and Sweden). Historical records tell of a range of different types adapted to climate and varying cultivation practices. Genetic analyses of genebank maintained landrace rye have yet failed, with a few exceptions, to detect differentiation between rye types. Concerns have been raised that genebank material does not truly reflect the historical variation in landrace rye. In this study, we have therefore genotyped old and historical samples of rye as well as extant material. Two historical seventeenth century samples were obtained from a grave and a museum archive respectively, and 35 old samples were taken from 100 to 140-year-old seed collections and museum artefacts made of straw. We could confirm the results of previous studies suggesting Fennoscandian landrace rye to be one major meta-population, genetically different from other European rye landraces, but with no support for slash-and-burn types of rye being genetically different from other rye landraces. Only small differences in genetic diversity and allele distribution was found between old landrace rye from museum collections and extant genebank accessions, arguing against a substantial change in the genetic diversity during twentieth century cultivation and several regenerations during genebank maintenance. The genotypes of the old and historical samples suggest that the genetic structure of Fennoscandian landrace rye has been relatively stable for 350 years. In contrast, we find that the younger samples and early improved cultivars belong to a different genetic group, more related to landraces from Central Europe.

Highlights

Rye (Secale cereale L.) has for centuries, along with barley (Hordeum vulgare L.), been a main crop for human consumption in Northern Europe (JuhlinDannfeldt 1926; Behre 1992; Leino 2017)
These were of two origins; 24 accessions from historical seed collections originating from the late nineteenth and early twentieth century (Leino et al 2009) (Fig. 1a) while the remaining grains were found in eleven straw artefacts, such as Christmas decorations, collected in late nineteenth and early twentieth century (Fig. 1d)
Individuals with 10% or more missing data were excluded from the analysis

Summary

Introduction

Rye (Secale cereale L.) has for centuries, along with barley (Hordeum vulgare L.), been a main crop for human consumption in Northern Europe (JuhlinDannfeldt 1926; Behre 1992; Leino 2017). Rye has been cultivated on fertilized permanent fields as well as in slash-and-burn cultivation where rye was the main crop. Several historical records from the sixteenth to the early twentieth century tell that a specific type of rye (‘‘tuvrag’’, ‘‘rotrag’’, ‘‘fallerag’’) was used for slash-and-burn cultivation (Tvengsberg 1995; Ahokas 2012; Leino 2017). Other historical records instead state that the same type of rye was sown on the swidden as in the fields (Leino 2017). This conflict between records is still unsolved and may be explained by different traditions in separated regions. Some historical records state that the harvest from slash-andburn cultivation was seen as excellent seed for sowing in the permanent fields As the historical records regarding rye in the slashand-burn cultivation system are ambiguous, genetic

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