Abstract

Landraces are local populations of crop plants adapted to a particular environment. Extant landraces are surviving genetic archives, keeping signatures of the selection processes experienced by them until settling in their current niches. This study intends to establish relationships between genetic diversity of barley (Hordeum vulgare L.) landraces collected in Spain and the climate of their collection sites. A high‐resolution climatic data set (5 × 5 km spatial, 1‐day temporal grid) was computed from over 2,000 temperature and 7,000 precipitation stations across peninsular Spain. This data set, spanning the period 1981–2010, was used to derive agroclimatic variables meaningful for cereal production at the collection sites of 135 barley landraces. Variables summarize temperature, precipitation, evapotranspiration, potential vernalization and frost probability at different times of the year and time scales (season and month). SNP genotyping of the landraces was carried out combining Illumina Infinium assays and genotyping‐by‐sequencing, yielding 9,920 biallelic markers (7,479 with position on the barley reference genome). The association of these SNPs with agroclimatic variables was analysed at two levels of genetic diversity, with and without taking into account population structure. The whole data sets and analysis pipelines are documented and available at https://eead-csic-compbio.github.io/barley-agroclimatic-association. We found differential adaptation of the germplasm groups identified to be dominated by reactions to cold temperature and late‐season frost occurrence, as well as to water availability. Several significant associations pointing at specific adaptations to agroclimatic features related to temperature and water availability were observed, and candidate genes underlying some of the main regions are proposed.

Highlights

  • Landraces are populations of crop plants adapted to a particular environment, through a long history of cultivation by local farmers (Zeven, 1998)

  • Several significant associations pointing at specific adaptations to agroclimatic features related to temperature and water availability were observed, and candidate genes underlying some of the main regions are proposed

  • We believe the processes that have shaped the diversity of Spanish barleys are typical of the expansion of crops outside their centres of origin, and that these analyses provide a case in point for the usefulness of environmental association analysis (EAA) to shed light on adaptation processes affecting crop landraces. 107 MATERIALS AND METHODS

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Summary

INTRODUCTION

Landraces are populations of crop plants adapted to a particular environment, through a long history of cultivation by local farmers (Zeven, 1998). The Spanish Barley Core Collection (SBCC) was compiled as a balanced representation of the crop cultivated in the country until the second half of the 20th century (Igartua et al, 1998) It has been studied extensively, showing distinct agronomic and genetic features that highlight its interest as research tool for pre-breeding and gene mining (Igartua et al, 1998). We first tested the relationship of the distribution of germplasm groups detected through population structure analysis and their genetic polymorphisms to agroclimatic variables We expected that these analyses would point at genomic regions that have driven the adaptation and differentiation of germplasm groups reflecting their history of evolution in distinct agro-ecological areas. We believe the processes that have shaped the diversity of Spanish barleys are typical of the expansion of crops outside their centres of origin, and that these analyses provide a case in point for the usefulness of environmental association analysis (EAA) to shed light on adaptation processes affecting crop landraces

107 MATERIALS AND METHODS
Findings
501 DISCUSSION
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