Cultivar-by-management interaction effects on timothy yield and quality evaluation

Abstract

Timothy (Phleum pratense L.) is the most important cultivated grass in eastern Canada. Cultivars from many parts of the world are evaluated and grown under different management regimes throughout the eastern region. This implies potentially large biased cultivar performance estimates due to potential cultivar-by-management interactions. A trial of 16 timothy cultivars was seeded at two locations in 1985 and submitted to two harvest management regimes to evaluate the magnitude of the cultivar-by-management interaction and cultivar stability. In this trial, dry matter production, acid detergent fibre, neutral detergent fibre and crude protein were evaluated during a 3-yr period. Results indicate large cultivar-by-management, cultivar-by-location, and cultivar-by-year interactions for most parameters. Cultivar by management was generally the largest interaction with very low correlations between contrasting managements at the first harvest. However, stability parameter analysis indicated that most cultivars were stable. The determination of the contribution of the different cultivars to the interaction effects using orthogonal contrasts appeared to be the most meaningful technique for stability analysis and should be favoured in the determination of cultivar performance constancy. This technique allows one to define precisely the magnitude of the effect of each cultivar for each interaction and appeared very powerful in identifying stable cultivars. Key words: Timothy, Phleum pratense, stability analysis, genotype by environment interaction