The contribution of perennial ryegrass (Lolium perenne L.) breeding to whole pasture productivity under dairy cattle grazing in New Zealand. 2. Rates of gain in production traits and economic value

Abstract

Perennial ryegrass (Lolium perenne) plant breeding has delivered several high performing and broadly adapted cultivar‐endophyte (Epichloë) combinations for the New Zealand pasture‐based livestock industries. However, the trends in key traits and the potential economic value being added to farm systems have not previously been addressed systematically. Rates of gain in yield, nutritive value, phenological and morphological traits, and the economic value of those traits, were estimated among and within ryegrass functional groups (heading date, ploidy) traded commercially between 1973 and 2012. Whole pasture dry matter yield improvements of c. 80 and 60 kg DM/ha per year were identified in in late‐season heading diploids and tetraploids respectively. Trends in metabolisable energy were negative within functional groups, but positive when all cultivar‐endophyte combinations were included in the analysis due to the addition of tetraploids and late‐season heading diploids from the mid‐1990s. The estimated trend in overall economic value (all cultivar‐endophyte combinations included) was $7/ha per year based on DM yield only, about half the rate of gain previously estimated using small‐plot merit testing data. The trend increased to $15/ha per year when ME was included due to the emergence of commercial tetraploids from the early 2000s onwards. Estimated economic gains were high within late‐season heading diploids and tetraploids but not mid‐season diploids. These trends suggest that, if high performing cultivar‐endophyte combinations had been adopted in New Zealand dairy systems, then pasture utilization should have increased by ~1 t DM/ha above the current industry average. Reasons for this apparent discrepancy are discussed.

Effects of heading date and Epichloë endophyte on persistence of diploid perennial ryegrass (Lolium perenne). 1. Heading date

“…It is estimated that plant breeding has led to increases in genetic gain for a variety of traits of >1% per year in New Zealand, with recent breeding focusing on the production of late-heading cultivars as well as early-and mid-heading cultivars (Woodfield and Easton 2004;Lee et al 2012). Improvements in traits include increases in DM production and nutritive value (Chapman et al 2023b). These improvements are consistent with the greater persistence of the two late-heading cultivars in our study, both of which are more recent than the two mid-heading cultivars.…”

Epichloë fungal endophyte interactions in perennial ryegrass (Lolium perenne L.) modified to accumulate foliar lipids for increased energy density

“…Continuing improvements through plant breeding are essential to the enhancement of on-farm productivity for this species. Annual genetic gains ranging from 0.3 to 0.75% have been reported for traits such as dry matter yield and nutritive value through conventional breeding programmes, and this has resulted in the release of many commercial cultivars over the past four decades [ 2 , 3 ]. However, it is also recognised that biotechnology holds the promise of providing rapid additional genetic gain in this species through the introduction of novel traits [ 4 ].…”