Differences between spring wheat cultivars in early growth

Summary Twelve spring wheat cultivars were grown as isolated plants in the field and their pre-anthesis growth was interpreted in terms of plant growth analysis. Relative growth rate (RGR) decreased steadily with time due to a decline of leaf area per unit plant weight (LAR), which could be explained by the reduction of the portion of leaf weight in total plant weight (LWR). Growth per unit leaf area (NAR) and leaf area per unit leaf weight (SLA) changed only little with time.Differences between cultivars for NAR and LAR were of similar magnitude: both 8% when measured by the genetic coefficient of variation. Because both quantities were negatively correlated, the genetic variation of RGR was only 5%. Genetic variation for LWR and SLA were also of similar size, both about 4%. Estimates of genetic variances and covariances based on cultivar means appeared to be biased strongly when the error variation of the means was neglected.Special attention is paid to the methodology of plant growth analysis.