Using Leaf-Area Expansion Rate To Improve Yield of Tall Fescue

Summary Several physiological characters have been proposed for use in breeding programs for higher yield potential. Our objectives were to evaluate recurrent restricted phenotypic selection for developing populations of tall fescue (Festuca arundinacea Schreb.) for low and high rates of leaf-area expansion (LAE). After four cycles, LAE was 181 and 74 mm²/day for the high (H) and low (L) populations, respectively. It appeared that LAE changes in early generations were due largely to increased leaf elongation rate (LER) of the H populations, whereas later progress was due largely to decreased leaf width (LW) of the L populations. Overall, LER had a larger effect on LAE than did LW. Number of tillers/plant was inversely related to LAE. In field plots, yield of vegetative regrowth of the L₄ population was 25 % lower than that of the control (C₀) population because the 2.1-fold increase in tiller density was more than offset by the 2.8-fold decrease in weight tiller. Tiller density was not reduced by selection for high LAE; in fact, the H₂ population yielded 39 % more than the C₀ population because both tiller density and weight/tiller were increased about 20%. Later generations were lower yielding than the H₂ population, but higher yielding than the C₀ population. The H₂ population was superior, perhaps due to a complementary mixture of large and small plants. Alternatively, inbreeding depression may have limited further genetic advancement. Yields of Kenhy and Mo-96 were similar, while that of Ky-31 was lower than those of the C₀ population. Photosynthesis of single leaves was altered less than 10% by selection.