Response to Selection for Leaf Area Expansion Rate of Tall Fescue1

Abstract

Development of effective selection criteria for the improvement of dry matter yield is a desirable goal in forage grass breeding. Leaf area expansion rate (LAER) has been suggested as acceptable selection criterion for improving post‐flowering yield of tall fescue (Festuca arundinacea Schreb.). Our objectives were to evaluate the responses of LAER, and its components leaf elongation rate (LER) and leaf width (WID) to five cycles recurrent phenotypic selection for both high and low LAER. In August 1980, a representative Co population, parents and offspring of the third and fifth cycles of selection for high and low LAER, and the check cultivars Missouri 96 and Kentucky 31 were transplanted into a field experiment. One tiller on 40 plants of each entry was evaluated in the fall of 1980 and 1981 for LER, WID, and LAER. Linear regression of performance on cycle of selection predicted an increase in LER of 0.87 and 0.48 mm/day/cycle of selection for high LAER in 1980 and 1981, respectively, while selection for low LAER resulted in a predicted decrease in LER of 0.77 and 0.84 mm/day/cycle of selection in 1980 and 1981, respectively. Predicted increase of WID was 0.45 and 0.33 mm/cycle in 1980 and 1981, respectively. Response of LAER to selection for high LAER in 1980 and 1981 was an increase of 15.7 and 10.8 mm2/day/cycle of selection, respectively, while selection for low LAER caused LAER to decrease by 11.6 mm2/day/cycle of selection in 1980 and 10.5 mm2/day/cycle in 1981. In both years, the responses of LER, WlD, and LAER to divergent selection for LAER were largely linear and symmetric. Thus, gene action for LAER and its components is additive in large part, and it is likely that continued response to selection would be realized in additional cycles.