Submitted to: Crop Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: October 10, 2007
Publication Date: March 1, 2008
Citation: Waldron, B.L., Robins, J.G., Peel, M., Jensen, K.B. 2008. Genetic Estimates for Forage Yield and Nutritional Quality of Tall Fescue Grown Under Spaced Plant and Sward Conditions. Crop Sci. 48: 443-449 Interpretive Summary: Most forage breeding programs have utilized spaced plant nursery evaluations to select breeding materials. However, the ability of spaced plants to predict sward yield has been questioned. The role of spaced plants versus swards in tall fescue breeding has not been reported. The objective of this paper was to compare genetic parameters and the efficiency of indirect selection using spaced plants to improve sward yield and nutritional quality in tall fescue. Results showed lack of correlation and inconsistent rankings between spaced plants and sward conditions for forage yield, plant height, tiller density, crude protein, and many fiber traits. There was agreement between the spacings for leaf softness, lignin, and digestibility; however, it was always more efficient to directly select for these traits using sward conditions. We conclude that spaced plant evaluation will be less effective (possibly ineffective) at improving sward yield and CP, and only moderately predictive of sward leaf softness and some fiber and digestibility traits in tall fescue. While this is the first report of this kind in tall fescue, our results are in agreement with many other cool-season grass studies dating back as far as the 1940s. One must wonder why the continued predominant use in grass breeding of spaced plant nurseries to predict yield and nutritional quality. New research is needed to streamline forage breeding by finding evaluation conditions that maximize genetic expression, but are still predictive of actual sward production.
Technical Abstract: The validity of spaced plant evaluation to determine sward performance of forage grasses has oft been questioned. This experiment studied the efficiency of spaced plant evaluation to indirectly improve sward yield and nutritional quality in tall fescue (Festuca arundinacea Schreb.). A tall fescue breeding population was evaluated in Logan, UT when grown in spaced plant and seeded plots. Narrow-sense heritabilities, genetic and rank correlations, and indirect selection efficiencies were estimated. Heritability for forage yield was similar between spaced plants and swards (0.43 and 0.44, respectively), but genetic correlation between the two was low (0.41 plus or minus 0.54) indicating that spaced plant selection would be ineffective at improving sward yield. The lack of significant relationship (r = 0.30) in family ranking between the two spacings, further suggested that spaced plants were not accurately predicting sward yield. Heritability of crude protein from swards was low (0.27 plus or minus 0.25) compared to a high heritability of 0.77 plus or minus 0.08 from spaced plants, but a negative genetic correlation existed between the two spacings (r = -0.11 plus or minus 0.49). For most fiber traits, heritabilities were similar between spaced plants and swards, with moderate to high genetic correlations, but rank correlations were often low and non-significant. Overall, indirect selection efficiencies and rank correlations of less than '1.0' suggested that direct selection using swards would be best to improve nuitritional quality of swards. Spaced plant evaluation appears to be less effective, or ineffective, at improving sward yield and nutritional quality in tall fescue. New techniques are needed that maximize genetic expression, but simulate actual sward production of forage grasses.