Does the "high sugar" trait of perennial ryegrass cultivars express under temperate climate conditions?

M Jordana Rivero,Cristian J Moscoso,Fabián Lukas Neumann,Oscar A Balocchi,Michael R F Lee,Juan Agustín Siebald,Don Meyer

doi:10.1111/gfs.12406

Abstract

The objective was to evaluate water‐soluble carbohydrate (WSC) and crude protein (CP) concentration of perennial ryegrass (PRG) cultivars with different genetic potential for producing WSC under two contrasting agronomic managements in temperate climate (southern Chile). A 4 × 2 factorial design was randomly allocated to 24 plots (31 m2 each, three blocks): four PRG cultivars (diploid standard cultivar, “2nSt”; tetraploid standard cultivar, “4nSt”; diploid high sugar cultivar developed in New Zealand, “2nHSNZ”; and tetraploid high sugar cultivar developed in Europe, “4nHSEU”) and two agronomic managements (“favourable,” defoliations at three leaves per tiller and nitrogen (N) fertilization rate of 83.3 kg N ha−1 year−1; “unfavourable,” defoliations at two leaves per tiller and N fertilization rate of 250 kg N ha−1 year−1). Herbage samples were collected in early spring, spring, summer and autumn. Concentration of WSC did not differ among cultivars in spring and summer, averaging 194 and 251 g/kg DM, respectively. The cultivar 4nHSEU had the greatest WSC concentration in early spring and autumn (187 and 266 g/kg DM, respectively) and the greatest CP concentration across samplings (average 230 g/kg DM). Favourable management improved WSC concentrations in early spring and summer and decreased CP in spring, summer and autumn. Annual DM yield did not vary with cultivar or management, averaging 8.43 t/ha. Within a 12‐month study at one site in a temperate environment in southern Chile, PRG cultivars have not shown a consistent expression of the “high sugar” trait, where a genetic × environment interaction might be operating.

Highlights

Perennial ryegrass (Lolium perenne L.) is the forage species most widely used in temperate pastures (Wilkins & Humphreys, 2003) as it grows well in a wide range of soil fertility situations, is easy to establish and manage (Charlton & Stewart, 1999), with high forage yields, digestibility and adaptation to a range of practices (McDonagh, O'Donovan, McEvoy, & Gilliland, 2016)
Crude protein and water-soluble carbohydrate (WSC) contents vary markedly with season, with crude protein (CP) peaks during autumn and early spring (Roche et al, 2009), whereas WSC accumulate throughout summer and autumn, leading to the highest total accumulated during winter and minimum values during early spring (Pollock & Jones, 1979)
Our findings show that it is not possible to increase the WSC to CP ratio in early spring above 0.7, and this is due to the extremely high CP concentration at this critical time of the year

Summary

Introduction

Perennial ryegrass (Lolium perenne L.) is the forage species most widely used in temperate pastures (Wilkins & Humphreys, 2003) as it grows well in a wide range of soil fertility situations, is easy to establish and manage (Charlton & Stewart, 1999), with high forage yields, digestibility and adaptation to a range of practices (McDonagh, O'Donovan, McEvoy, & Gilliland, 2016). Crude protein and WSC contents vary markedly with season, with CP peaks during autumn and early spring (Roche et al, 2009), whereas WSC accumulate throughout summer and autumn, leading to the highest total accumulated during winter and minimum values during early spring (Pollock & Jones, 1979). These variations in nutritive components throughout the year lead to an imbalance between readily available energy, in the form of WSC, and nitrogen in the rumen

Objectives

Findings

Discussion

Conclusion