Mega-environment investigation in durum wheat yield trials in Iran

Mega-environment (ME) investigation and genotype evaluation are among the most important objectives of multi-environment trials. This study aims to investigate the possible existence of meaningful mega-environments and identify high-yielding and stable genotypes for rainfed durum wheat-growing regions. The GGE (genotypic main effect plus genotype-by-environment interaction) and GGL (genotypic main effect plus genotype-by-location interaction) biplots analyses were applied to durum wheat grain yield data from multi-year trials conducted at six locations differing in climatic conditions across Iran. Yearly multi-location analysis of variance for grain yield revealed that the location was the main source of variation and captured for 78.5–89.8% of total variation and the GL interaction, depending on year, was greater 2.8–4.4 times than genotype effect alone. The collective analysis of yearly GGL biplots revealed repeatable locations grouping across years and showed that the durum wheat growing region can be divided into four MEs: the western ME represented by the moderate cold location, southern-west ME represented by moderate warm location, western-north ME and eastern-north ME both represented for cold locations. The results suggest that durum wheat yield trials should be conducted and genotype recommendation be made according to each ME. The evaluation of genotypes for mean yield and stability performance per each ME, recommended the breeding line G14 for each both western and western-north MEs, breeding line G10 for southern-west ME and breeding line G3 for eastern-north ME. Based on the factorial regression analysis, climatic variables of monthly rainfall in March (17.5%), May (9.5%), June (7.9%), April (6.8%), cumulative rainfall (12.5%), and average temperature of January (6.6%) significantly ( P < 0.01) affected genotypes performance and contributed to 60.8% of total GE variation. The results confirmed four different mega-environments in durum wheat yield trials, suggest genotype recommendation should be made according to each mega-environment.