SPECIAL REPORT
RYEGRASS
Endophytes key to ryegrass success Words by: Sheryl Haitana
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or large parts of New Zealand, ryegrass is still indisputably hard to beat, PGG Wrightson Seeds chief scientific officer Dr Alan Stewart says. Perennial ryegrass is the major grass species used in dairy farms across most regions of NZ. It is rapid to establish, very grazing tolerant, mixes well with white clover and produces large quantities of palatable feed. However, it is not perfect and factors such as droughts, pests and climatic extremes can limit its persistence. This is particularly apparent in northern regions. The increase in the stocking rate in the dairy industry over the last 20-30 years and the amount of herbage consumed by animals has put added pressure on pastures and impacted persistence. It has limited seed drop and recruitment of new plants into the pasture. Plant breeders have continued to make gains in yield, but also focus on quality, persistence, disease resistance and pest tolerance through endophytes. Perennial ryegrass requires endophytes in order to resist pest effects over large parts of the country as without endophyte, ryegrass can struggle to persist. Incorporating endophytes into ryegrass adds further complexity to breeding programmes. “We are continuing to develop new endophytes to have them capable of combating particular pests,” Alan says. New technologies carried out by AgResearch like gene editing are likely to provide improved endophyte strains for the future.
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Breeding research on ryegrasses.
Breeding pasture plant cultivars in NZ involves breeding many types with specific roles on farms. These include a range of perennial ryegrasses, diploids and tetraploids, with earlier or later flowering behaviour. In addition farmers require hybrid ryegrasses, Italian ryegrasses and annual ryegrasses. Then we also have to produce the clovers and herbs for these mixtures as well as chicory, plantain and the numerous forage brassica systems that get used in NZ farming systems. Breeding other species for drought and heat tolerance is crucial with options like tall fescue, cocksfoot and lucerne providing important roles. It would be a lot easier if all the investment could be in one type of ryegrass, but farmers require a diversity of pastures for their farm systems around NZ, Alan says. About $40 million/year is invested in the plant breeding industry
across all species. Few cultivars are developed in less than 10 years and each cultivar costs more than $1m before it reaches the market. To improve persistence, breeders select plants and endophytes under the most stressful conditions of drought, grazing and insect pressure, across different soils around NZ with a particular focus on northern regions. Breeders evaluate performance over many years and under varying grazing conditions. Parent plants for cultivars need to be proven over four or five years before they are selected for future breeding programmes. Genomic selection is starting to be applied by PGG Wrightson Seeds in both ryegrass and clover breeding in NZ, which could accelerate selection, but it takes time to get the systems working, to get scale and experience, Alan says. “I’m confident that it will be used more and more as time goes by. But it’s
Dairy Exporter | www.nzfarmlife.co.nz | November 2021
