Fructan synthesis, accumulation, and polymer traits. I. Festulolium chromosome substitution lines.

Joe A Gallagher,Adam Charlton,Lesley B Turner,Peter Williams,David Thomas,Andrew J Cairns

doi:10.3389/fpls.2015.00486

Abstract

The fructans found as storage carbohydrates in temperate forage grasses have a physiological role in regrowth and stress tolerance. They are also important for the nutritional value of fresh and preserved livestock feeds, and are potentially useful as feedstocks for biorefining. Seasonal variation in fructan content and the capacity for de novo fructan synthesis have been examined in a Festulolium monosomic substitution line family to investigate variation in the polymers produced by grasses in the ryegrass-fescue complex. There were significant differences between ryegrass and fescue. Fescue had low polymeric fructan content and a high oligomer/polymer ratio; synthesis of polymers longer than degree of polymerization 6 (DP6) from oligomers was slow. However, extension of polymer length from DP10/DP20 upward appeared to occur relatively freely, and, unlike ryegrass, fescue had a relatively even spread of polymer chain lengths above DP20. This included the presence of some very large polymers. Additionally fescue retained high concentrations of fructan, both polymeric and oligomeric, during conditions of low source/high sink demand. There were indications that major genes involved in the control of some of these traits might be located on fescue chromosome 3 opening the possibility to develop grasses optimized for specific applications.

Highlights

The fructan polymers found as storage carbohydrates in temperate forage grasses (Pollock and Cairns, 1991) have widely reported physiological roles in regrowth and stress tolerance (Vijn and Smeekens, 1999; Chalmers et al, 2005)
Third order polynomial curves were the best fit for disaccharide and monosaccharide sugars, but fourth order equations improved the fit for total water-soluble carbohydrate (WSC), polymeric fructan and oligomeric fructan (Table 1)
There were no significant differences between the different substitution lines in curve form, indicating that the seasonal pattern was consistent

Summary

Introduction

The fructan polymers found as storage carbohydrates in temperate forage grasses (Pollock and Cairns, 1991) have widely reported physiological roles in regrowth and stress tolerance (Vijn and Smeekens, 1999; Chalmers et al, 2005). Grasses from the ryegrass-fescue complex are well suited to the prevailing climatic conditions in many temperate regions (Wilkins and Humphreys, 2003) but do differ in nutritional value and stress tolerance. Fescues generally have lower nutritional value, but greater stress tolerance and will grow on more marginal land (Thomas and Humphreys, 1991; Humphreys et al, 1997). Fructan polymer metabolism in Festulolium and in the UK around 75% of feed requirements for cattle and sheep are obtained from such grasses (Wilkins and Humphreys, 2003). In the future they have the potential to be useful as feedstocks for biorefining as there is an increasing demand to move from oil-based processes to sustainable carbohydrate-based processes (Van Ree and Annevelink, 2007)

Methods

Results

Conclusion