Interrelationships between Rates of Leaf Appearance and Tillering in Selected Tall Fescue Populations1

Abstract

Tiller density and yield/tiller are yield components associated with dry matter productivity of grasses. Breeding programs may benefit by exploiting the mechanisms that control growth and development of these components. Our objective was to evaluate the relationship between leaf appearance and tillering in seedlings of tall fescue (Festuca arundinacea Schreb.). Plants were fourth‐cycle progeny from a recurrent restricted phenotypic selection program for high (H) and low (L) rates of leaf area pansion. Four half‐sib populations were used to represent each selection direction. Seedlings were grown in a controlled‐environment chamber for 12 weeks at 25/20°C and a 14‐h photoperiod. Photosynthetic photon flux density was 500 μmol m−2 s−1. Plants remained vegetative during the growth period. In general, there were few differences among L or among H populations for the characters measured. Herbage yield of the H populations averaged 12% greater than that for the L populations. Relative tillering rate (tillers/tiller/day) for the L populations was 32% greater than for the H populations. The L populations had a 12% greater appearance rate of fully‐collared leaves on each tiller, and consequently, more potential sites available for tillering. They also had 11% greater utilization of tillering sites than did the H populations. Collectively, data showed differential genetic control of tillering rate in these contrasting populations. Tillering rate was not dependent on concentration of water‐soluble carbohydrates in leaf, root, and especially stem base tissues as concentrations were less in L than in H populations. Leaf elongation rate and yield/tiller were positively associated with herbage yield. The H populations averaged 28% greater in specific leaf weight than the L populations. Specific leaf weight was positively associated with yield/tiller and herbage yield. Carbon dioxide exchange rate of single leaves was not altered by selection. Genetic improvement of both tiller weight and tillering rate may be difficult using simultaneous selection.