Genetic origins of perennial ryegrass (Lolium perenne) for New Zealand pastures

Abstract

New Zealand perennial ryegrass germplasm originated largely from seed introduced from the UK during the 1800s. Modern breeding began in the 1930s and soon utilised selections from the best ecotypes as "mother" seed for the seed industry and after numerous reselections this resulted in the release of Grasslands Ruanui 1955. Winter growth was improved by hybridising with Italian ryegrass to produce the "short rotation hybrid" cultivar Grasslands Manawa, released in 1943. Further introgression to perennial ryegrass led to the development of Grasslands Ariki "long rotation hybrid", functionally a perennial, released in 1965. The identification of a valuable ecotype from the Mangere district in Northern New Zealand in the late 1960s had a substantial impact on ryegrass breeding in New Zealand and has subsequently been widely used in all Australasian ryegrass breeding programs. Germplasm from mild oceanic regions of North West Spain, collected in the 1980s, has provided a valuable combination of winter growth with late flowering behaviour. This has been used in many recent breeding programs. Considerable research has gone into endophytes of ryegrass to develop safe and persistent pastures. The lack of chemical diversity within endophytes of New Zealand ecotypes has required considerable sourcing of overseas germplasm for endophyte discovery. In recent years breeders have introgressed a wider range of germplasm, including winter active Mediterranean material, cold tolerant Northern European material, as well as Italian ryegrass and meadow fescue. Tetraploid perennial ryegrass cultivars have been released in the last 20 years, based largely on New Zealand diploid cultivars but also using some European tetraploids. Today a full range of cultivars from early flowering diploids to late flowering tetraploids is available to the farming industry. The use of a wider range of germplasm is discussed in relation to advances in our knowledge of genetic origins of perennial ryegrass. Genetic advances should be achievable from more diverse germplasm by using a combination of traditional breeding techniques and new technologies, such as marker assisted selection. However, lifting overall pasture performance still remains a challenge as ryegrass cultivars are used in mixtures with white clover and any increase in the ryegrass yield is often partially cancelled by decreased clover yields

Genetic gain in perennial ryegrass forage yield in Australia and New Zealand

“…The data set represents all major germplasm types (i.e. New Zealand, European and in particular north-west Spain) (Stewart 2006), diploids and tetraploids, various heading dates (early to late) and contain all locally commercialised endophytes. The cultivars marketed in Australia that were not included were functionally similar to the low yielding Australian naturalised ecotypes 'Victorian' and 'Kangaroo Valley'.…”

“…The forage yield and persistence of Australasian ryegrass cultivars is due to a combination of plant genetics and novel endophytes giving superior pest resistance (Hume & Sewell 2014). Before the discovery of the role of endophyte in ryegrass staggers in grazing animals, and the role of the alkaloids produced by the endophyte in pest protection, the endophyte status of cultivars confounded interpretation of cultivar performance (Stewart 2006). Endophyte status was not considered and therefore not monitored in breeding programmes or in seed sold on the Australasian market.…”

Persistence of dry matter yield among New Zealand perennial ryegrass (Lolium perenne L.) cultivars: insights from a long-term data set

“…Henceforth, all entries are simply referred to as "cultivars". Details of the breeding history of all of the cultivars can be found in Stewart (2006). 'Ruanui' (released in the 1960s) and 'Nui' (1970s) were the oldest entries in the trial: all other cultivars were released in the 1990s and 2000s.…”

“…The experiment reported here compared a wide range of perennial ryegrass functional types (diploids and tetraploids; early to very late maturity dates) and genetic backgrounds (including New Zealand and Australian ecotypes; southern and northern European material; and some cultivars including Italian ryegrass and meadow fescue parentage). Many were based on the old Hawke's Bay and Mangere ecotypes that have been widely used in perennial ryegrass breeding programmes for many decades (Stewart 2006), and will continue to be used because of their strong adaptation to New Zealand conditions (Easton et al 2011).…”

Differences in nitrogen uptake and marginal yield response between low and high yielding perennial ryegrass (Lolium perenne) genotypes

“…As the majority of trials informing current recommendations were undertaken before the late 1990s, most data contributing to Australian and New Zealand industry best practice can only have been derived from European ecotypes naturalised to local environments, such as ecotype Victorian and the cultivars 'Grasslands Ruanui' and 'Grasslands Nui'. These ecotypes (genotypes naturalised to an environment) and the cultivars (marketed genotypes) derived from them are comparatively winter dormant when compared to modern northwest Spanishderived cultivars (Stewart 2006). Australian ecotypes are also semi-summer dormant with poor late spring, summer and autumn growth.…”