|Graybosch, Robert - Bob|
Submitted to: Crop Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/3/2006
Publication Date: 4/25/2006
Citation: Mishra, R., Baenziger, P.S., Russell, W.K., Graybosch, R.A., Baltensperger, D.D., Eskridge, S.M. 2006. Crossover interactions for grain yield in multienvironmental trials of winter wheat. Interpretive Summary: Wheat breeders face a continuous dilemma, namely, should one test experimental lines in relatively few environments, and hope the results predict performance across a wide range of commercial production zones, or, as environments have such a large year-to-year effect on the performance of lines in breeding programs, does one need to test and make selections from a wide range of environments. Ideally, the latter option would be followed. However, limited resources prevent exhaustive testing. This paper reports the results of studies designed to determine whether sampling of limited environments during breeding programs is useful in prediction of performance across a multitude of environments. Cross-over-interactions, or changes in performance (grain yield) rank across diverse environments, were determined. Such interactions were fairly common. A prudent breeding approach would be to identify the best lines on the basis of mean performance across all environments and then from among those select the lines involved in the fewest number of significant cross-over-interactions. For example, in 1998, the check ‘Abilene’ and experimental line NI97405 had nearly identical mean yields and were among the best 15% of the lines, but Abilene was involved in substantiallyfewer significant COIs than was NI97405. Abilene should be favored over NI97405, as it promises more stable and predictable production across a wide range of environments.
Technical Abstract: Crossover interactions (COIs) are changes in ranks among cultivarsacross environments. Breeders are concerned about COIs because their frequency affects how well rankings from one environment predict rankings in another environment. This research was undertaken to determine the frequency and distribution of COIs for grain yield within years in two regional trials of winter wheat (Triticum aestivum L.). The trials were in Nebraska and in the south-central USA (SCUS). Each trial had four environments per year, and results from 1998, 1999, and 2000 were considered. Significance of COI for each pair of lines in each pair of environments within years was determined by a t test withan interaction-wise Type 1 error rate. Grain yield varied significantly across environments in both trials in all years, and in the within-year analyses the line X environment interaction was always highly significant. In the Nebraska trial, the frequency of COIs was less than expected by chance only in one pair of environments in 1 yr. Nonetheless, because estimates suggested the line X environment X year variance was substantially greater than the line X environment variance, this significant occurrence of COIs did not support breeding for local adaptation. In the SCUS trial, a lower frequency of COIs occurred than in the Nebraska trial. In both trials, frequency of COIs in a pair of environments was not closely related to the difference in mean yield between those environments, which raised the usefulness of categorizing environments as low-stress or as high-stress for the purpose of selection.