Relationship of Leaf Elongation to Forage Yield of Tall Fescue Genotype1

Abstract

Forage yield is usually not closely related to CO2 exchange rate of single leaves, and existing data suggest other factors such as canopy characters need to be studied. Therefore, we investigated the relationship between leaf elongation rate and forage yield of 14 genotypes of tall fescue (Festuca arundinacea, Schreb.). Plants were grown in the field under summer water stress and with irrigation. Leaf elongation 4, 8, or 16 days after defoliation was related positively to forage yield at the subsequent harvest during the post‐flowering period. Generally correlations with yield were best (r ≥ 0.67 in 11 of 14 sampling periods) for the 16‐day elongation measurement. Significant differences in leaf elongation at 16 days were noted among genotypes for each of the sampling periods for both irrigated and water‐stressed treatments. Differences among genotypes in leaf elongation were not always consistent from date to date indicating some genotype by environment interaction for this character. Range in leaf length and variance attributable to clones were greater under irrigation which suggested that selection would be more efficient with a good growing environment. Broad‐sense heritabilities for leaf elongation at 16 days calculated for data pooled over 2 years were 0.87 and 0.88 for the water‐stressed and irrigated treatment, respectively. Amount of leaf elongation 12 to 16 days after cutting may be a good estimator of subsequent forage yield because it would indicate the degree of radiation interception during early stages of regrowth, and also the rate of achievement of the critical leaf area index. Leaf elongation rate may be an acceptable criterion for estimating regrowth vigor and yield potential of clones and populations in breeding programs.