Stratification of SADC regional sorghum testing sites based on grain yield of varieties

We applied sequential retrospective (SeqRet) pattern analysis to stratify sorghum variety testing sites according to their similarity for yield discrimination among genotypes using historical grain yield data from 147 multi-environment trials (METs). The trials were conducted at 38 sites in 10 countries of the Southern African Development Community (SADC) region during 1987/1988-1992/1993 and 1999/2000. The analysis for the 6 years 1987/1988-1992/1993, covering 34 sites, clustered these sites into 6 major groups with a model fit of R2 = 0.75. With additional data from the year 1999/2000, the SeqRet pattern analysis delivered a very similar clustering of the 34 sites, with the additional four sites in 1999/2000 properly classified with appropriate site groups (R2 = 0.74). The results suggest that future sorghum variety testing could be restricted to a few representative sites selected from within each of the six identified site-groups.