Evaluating perennial ryegrass cultivars: improving testing

Abstract

The agronomic performance of a range of perennial ryegrass cultivar-endophyte combinations was compared in 16 trials conducted at sites throughout New Zealand. Each trial was run for 3 years according to seed industry evaluation protocols, measuring variables including: dry matter (DM) yield (total annual and seasonal DM yield), ryegrass ground cover at the end of 3 years, susceptibility to plant pulling, and rust incidence. The change in DM yield over the 3-year term of each trial was also analysed. There were significant differences among cultivars in total annual DM yield, and in seasonal DM yield for each of the five periods of the year among which yield was split (winter, early spring, late spring, summer, and autumn). Mean annual yield declined between Year 1 and Year 3 in all regions except Taranaki, by between 0.8 t DM/ha (Canterbury) and 5.3 t DM/ha (Waikato). There were significant region, year, region × year, and cultivar × year interactions in yield change. Significant differences in ground cover score for perennial ryegrass at the end of 3 years were recorded among cultivars. However, these differences did not mirror on-farm observations of ryegrass persistence in the Waikato during the drought of 2007/08, suggesting that the standard trial protocols currently used do not adequately test persistence. It is recommended that industry cultivar testing needs to more accurately assess perennial ryegrass persistence, using new protocols including running trials on commercial farms, for more than 3 years, and using mixed swards. Genetic differences in persistence could be generated more quickly by choosing sites known to challenge perennial ryegrass growth and survival. Keywords: perennial ryegrass, cultivar evaluation, DM yield, persistence testing, plant pulling, rust

Establishing phenotypic performance of grass varieties on Irish grassland farms

“…With poor genetic gain being reported for traits associated with persistence, a focus must be placed on evaluation practices. Plot-based evaluations expose varieties to minimal levels of stress resulting in differing levels of persistence being achieved in cut plot and animal grazing managements of varieties over the same period (Kerr et al 2012).…”

“…Long-term studies under ‘commercial’ conditions need to be implemented to fully assess persistence (Wilkins & Humphreys 2003; Kerr et al 2012). By increasing the level of pressure imposed upon varieties, differences in their persistence should be identifiable at an earlier stage, allowing breeders to identify superior parent plants to develop improved varieties.…”

“…A commonly used measure of pasture persistence is DM yield stability (Kerr et al . 2012; Lee et al . 2017), as many swards may have a low density of tillers but yet support high levels of productivity due to reduced intra-plant competition.…”

“…A commonly used measure of pasture persistence is DM yield stability (Kerr et al 2012;Lee et al 2017), as many swards may have a low density of tillers but yet support high levels of productivity due to reduced intra-plant competition. Varieties such as AberGain, Astonenergy, Dunluce, Glenveagh, Kintyre, Twymax and Tyrella appeared to have good yield stability as their DM production increased year on year; the remaining varieties (each of which were diploid varieties) all experienced reduced DM production in either 2014 or 2015.…”

“…The question remains whether current evaluations provide breeders with adequate selection criteria and feedback to develop new grass varieties which are akin to the needs of modern grassland farmers. To overcome the limitations of simulated grazing studies and identify superior grass genotypes suited to grazing systems there is a need to establish trials which better simulate ‘commercial’ farm conditions for longer periods than current evaluation protocols (Kerr et al 2012). On-farm grass evaluations have been undertaken previously (Casler et al 1998), but across a small number of farms with multiple varieties sown in strips within the same paddock.…”