Evaluation of a durum wheat selection scheme under Mediterranean conditions: adjusting trial locations and replications

The effectiveness of a cultivar evaluation scheme is impeded by the cost of experimentation. The aim of this study was to explore whether the locations employed in durum wheat evaluation program in Greece constituted a mega-environment (ME) and to adjust the number of trial replications and locations for realizing an optimum heritability (H) of 0.75. The analysis was conducted for grain yield (GY), agronomic and quality parameters in a 10-year (2002–2011) dataset and included a variable across years, number of genotypes and locations. The GGE biplot analyses revealed that trial locations can be considered as a single, complex ME. The existence of the ME was also confirmed by the high H across locations. The number of replications and locations for realizing an optimum H for GY was five replications compared to the four currently used, and five locations in lieu of 3–4 now tested. Plant height in March, final plant height and days to heading required three replications and four locations, winter frost three and five, powdery mildew three and seven, stem rust five and nine, whereas lodging 10 replications and 10 locations, respectively. Regarding quality, thousand-kernel weight required four replications and three locations, whereas vitreous kernel percentage six and eight, grain protein concentration four and seven, black point percentage 17 replications and was of zero H across locations. Finally, for the traits assessed only across locations, ash content required seven, wet gluten content five while gluten index and β-carotene three locations.