Comparison of Direct and Indirect Selection Response for Forage Yield and Its Components in Tall Fescue under Normal and Water Stress Environments

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Breeding based on selection indices is an effective method for improving complex traits such as yield. To assess the efficiency of different selection methods, 50 genotypes of tall fescue (Festuca arundinace) were evaluated under two moisture conditions including full irrigation (normal environment) and deficit irrigation (stress environment). The experiment was conducted according to a randomized complete block design with three replications during 2009 and 2010. Selection indices were calculated based on Smith-Hazel and Pesek-Baker methods by five traits including number of stem per plant, leaf/stem ratio, plant height, percent of dry matter and crown diameter under both conditions in two forms (with and without dry matter yield). Also response to selection and relative selection efficiency were estimated for studied traits and dry matter yield. Results showed that genotypes with the highest number of stem, leaf/stem ratio, plant height, crown diameter and the lowest percent of dry matter had the highest yield potential. In Smith-Hazel index under both moisture conditions, dry matter yield and number of stem per plant had the highest gain, while in Pesek-Baker index, dry matter yield had a negative gain. Result indicated that Smith-Hazel index (with yield) had the most selection efficiency and can be used in tall fescue breeding programs.

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