Simultaneous Selection for Yield and Stability in Crop Performance Trials: Consequences for Growers

Utilization of genotype × environment (GE) interaction encountered in crop performance trials is an important issue among plant breeders and agronomists. Practical integration of yield and stability of performance has not been achieved. The purposes of this paper are (i) to examine consequences to growers when researchers commit Type I (rejecting the null hypothesis or Hₒ when it is true) and Type (accepting the Hₒ when it is false) errors under a yield-based, conventional selection method (CM) and a proposed method (yield-stability statistic or YSₜ) that uses GE interaction, and (ii) to show why a greater emphasis on the stability component would be advantageous to growers. A corn (Zea mays L.) dataset was used to compute the YSₜ and to estimate Type II error rates for overall mean yield comparisons and for the stability-variance statistic, σ²ᵢ(σ²ᵢ measures contribution of ith genotype to the total GE interaction) at different (Type I error rate) and δ (minimal detectable difference) levels. When pairwise yield comparisons are made, a higher level of a will not be as harmful to growers as a higher level of β (Type II) error rate). Since researchers would prefer to have power (1 - β) of a test between 0.70 and 0.80, choosing an α(1) level (one-tailed) between and 0.20 should be appropriate. If an α(1) value of 0.225 is selected δ between 1.0 and 1.4, the Type II error rate would be almost zero. For stability, the Hₒ tested was that yield means of a genotype in different environments were equal, i.e., σ²ᵢ = 0. A consequence of committing a Type I error would be that growers could miss using a stable cultivar, but a consequence of committing a Type II error can be disastrous for growers, as they could choose an unstable genotype and suffer economically. A greater emphasis on performance stability during selection would benefit growers. Approved for publication by the Director of the Louisiana Agric. Exp. Stn. as Manuscript no. 92-09-6337.