Agronomic trials at cool (Gore) and warm (Palmerston North) temperate sites in New Zealand tested ten United Kingdom-bred (six diploids, four tetraploids) and two New Zealand-bred diploid ('Bronsyn', 'Impact') perennial and long-term hybrid ryegrasses (Lolium perenne, L. boucheanum) over two trial periods. Dry matter (DM) yields and persistence were better at the cool site but differential expression among cultivars for water-soluble carbohydrates (WSC) and yields was small compared with the warm site. The tetraploid cultivars generally had the highest concentrations of WSC but also on occasions had higher levels of crown rust, moderate DM yields and poorer persistence compared with diploids. Two of the tetraploid cultivars will be of value for their high WSC and good agronomic performance at the cool site. Some of the diploid UK cultivars expressed higher WSC and had similar or higher annual DM yields than some of the NZ-bred cultivars, and had high levels of resistance to crown rust. Overall, differences among cultivars in expression of WSC were small. Some differences occurred for seasonal DM yields with some UK cultivars having lower winter yields.
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
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