Abstract

Plant carbohydrates are of increasing interest as renewable feedstocks to replace petrochemicals in the generation of fuels and production of high-value chemicals. Greater understanding of the genetic control of diversity in fructan synthesis and accumulation would facilitate more directed channelling of feedstock to process in a ryegrass biorefinery. Divergent populations produced by phenotypic selection for water-soluble carbohydrate content have been used to investigate relationships between traits, and to identify patterns of genetic differentiation which indicate genomic regions under high and low selection pressure. Selection for high water-soluble carbohydrate content was associated with increased synthesis of large fructan polymers and increased accumulation of above-ground plant biomass, particularly during spring. Three rounds of selection and two rounds of recombination resulted in widespread genetic differentiation across the whole genome, causing reduced allelic richness and increasing homozygosity at some loci. A smaller number of loci were shown to be subject to high selection pressure. Breeding material subjected to many years of selection for water-soluble carbohydrate also showed allelic differences which may reflect the consequences of high selection pressure at some of these same loci. However, some of the loci unaffected in the divergent selection experiment showed similar effects. This might arise from differences in linkage disequilibrium in these two sets of plant materials, but more likely from the different genetic background of the germplasm. This illustrates the complex nature of the water-soluble carbohydrate trait in perennial ryegrass.

Highlights

  • Plant carbohydrates are of increasing interest as renewable feedstocks to replace petrochemicals in the generation of fuels and production of high-value chemicals

  • The data presented here to examine the component sugars of the total water-soluble carbohydrate (WSC) pool in these plants are from single copies of the individual plants and for just the last generation at the end of the selection experiment, but comparable results have been observed for the previous C1 generation

  • Calculation of total WSC content for the three C2s populations from high-performance liquid chromatography (HPLC) data by summing the individual named peaks showed trends that repeat the effects from the previous analyses [7], except for a relative underestimation of the WSC content of the C2s+ population

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Summary

Introduction

Plant carbohydrates are of increasing interest as renewable feedstocks to replace petrochemicals in the generation of fuels and production of high-value chemicals. In many temperate regions of the world, a large proportion of land area is occupied by grassland. (2015) 8:77–90 for livestock production, and forage grasses, ryegrasses, have been improved to provide increased nutritional value. Considerable genetic variation for WSC is available in perennial ryegrass and has been characterised to some extent [1]. It is this variation that has enabled the recurrent selection breeding programme at Aberystwyth to realise significant gain in WSC content over the past 30 or so years [2, 3]. High-sugar grasses offer the potential to produce high sugar yield for biorenewable applications without major change to the landscape

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