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