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

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.

The Effect of Drying Methods on Water-Soluble Carbohydrates and Crude Protein Concentrations and Their Ratio in Two Perennial Ryegrass Cultivars

“…However, the year may have had a relevant effect in the study carried out by Loaiza et al [33] which could explain the lower values compared with the present study. Previous results in cultivars with different genetic potential for producing WSC were not consistent, and the use of favourable management (defoliation at the three-leaf stage, and N fertilization of 83.3 kg N ha −1 year −1 ) improved the WSC concentration only in early spring and autumn seasons [35]. Few studies comparing high sugar cultivars with standard cultivars in temperate climate conditions have been reported [35,36], but the expression of greater WSC concentrations in AberMagic has been confirmed in other cool temperate climates [37,38].…”

“…Similar results were also found with cultivar Alto AR1, where the WSC/CP ratio in early (August-October) and late spring (November-December) was 0.45 and 1.11, respectively. Conversely, when assessing perennial ryegrass cultivars with different potential for producing WSC, no effect of cultivar on WSC/CP ratio was found, however one of the agronomic managements used (defoliations at three leaves per tiller and N fertilization rate of 83.3 kg N ha −1 year −1 ) did improve the ratio in spring, summer and autumn seasons [35].…”

“…The development of varieties with enhanced levels of WSC and lower CP concentration may contribute to reducing N emissions to the environment while maintaining a greater level of animal production per hectare [53]. However, such cultivars might not consistently express the high sugar trait under certain environments [8,35]. Furthermore, high sugar grasses may have lower DM yields than standard cultivars [54][55][56].…”

Some challenges and opportunities for grazing dairy cows on temperate pastures

“…Nevertheless, even though Taweel et al (2005) and Miller et al (2001) did not find any effect of WSC content of zero-grazed forage on DMI, the latter reported an increase in digestible DMI and milk yield driven by an increase in DM digestibility of forage selected for greater WSC content. Moreover, genotype × environment interactions can operate in some agroclimatic conditions (Parsons et al, 2011;Rivero et al, 2019) which might prevent cultivars from expressing the high-WSC trait. Although genetic selection for improving DMI can be pursued, breeding new perennial ryegrass cultivars is a long-term process (15-20 years) and gains would take time to become evident.…”

“…Although genetic selection for improving DMI can be pursued, breeding new perennial ryegrass cultivars is a long-term process (15-20 years) and gains would take time to become evident. Moreover, genotype × environment interactions can operate in some agroclimatic conditions (Parsons et al, 2011;Rivero et al, 2019) which might prevent cultivars from expressing the high-WSC trait.…”