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Research article2012Peer reviewed

Effect of region on the uncertainty in crop variety trial programs with a reduced number of trials

Forkman, Johannes; Amiri, Saeid; Von Rosen, Dietrich

Abstract

Results from crop variety trials may vary between geographical regions because of differences in climate and soil types. Results are usually presented at regional level. To evaluate the importance of the regions used in the Swedish variety trial programs, we examined which regions produced similar levels of yield and similar ratios in yield between cultivars; the amount by which variance could be reduced by division into regions or clusters of regions; and the amount of trials per region and year, replicates per trial, and trials per year required in order to fulfill specifications on the precision of results. Yield data from spring barley and winter wheat trials performed during 1997-2006 were studied using cluster analysis and variance component estimation. The objectives were (1) to discuss the effects of regions on precision when the number of trials has decreased; (2) to demonstrate the method; and (3) to report the results obtained. In spring barley, clusters of regions produced different levels of yield, but similar yield ratios between cultivars. In winter wheat, clusters of regions giving different yield ratios were identified. When the option of a single analysis was compared with that of region-wise analysis, the reduction in variance with the former, due to the larger number of trials, outweighed the reduction in variance with the latter due to decreased random interaction between trials and cultivars.

Keywords

Cluster analysis; Crop variety evaluation program; Multi-environment trial; Replication; Sample size calculation; Soil-climate area; Variety trial

Published in

Euphytica
2012, Volume: 186, number: 2, pages: 489-500
Publisher: SPRINGER