Assessment of grain yield stability and adaptability of ranfed durum wheat breeding lines

Because of unpredictable conditions in Mediterranean environments, successful crop production requires improved adaptation and yield stability to mitigate major abiotic stresses such as drought and cold. Consequently, the objectives of genetic improvement should include obtaining genotypes with high potential yield and stability in unpredictable conditions. The main objective of this study was to evaluate grain yield stability and adaptability of 25 durum wheat genotypes grown at seven agricultural research stations (Kermanshah, Maragheh, Qamloo, Shirvan, Uromieh, Ardebil and Ilam) for three cropping seasons (2011-2013) using the univariate and multivariate statistical methods. The combined analysis of variance showed significantly differences among the main effects due to environment and genotype x environment (GE) interaction. GE interaction sum of square was 15 times larger than that for genotypes, suggests the possible existence of sub-environmental groups for the genotypes. Grouping of environments was not repeatable among the years. Many of the durum brreding lines exhibited a high combination of yield and stability across both drought and cold environments, comparable to check cultivars. Evaluation of genotypes based on phenotypic stability statistics showed that breeding lines G8, G2, G7 and G11 and Saji cultivar had the best level of combination of yield and stability performances. Graphic analysis of GE interaction using the GGE (G GE) biplot model indicated that the cold environments of Maragheh, Ardebil, Qamloo, Shirvan and Uromia differed from moderate cold and warm environments of Kermanshah and Ilam in identifying specific adapted genotypes. Breeding lines with high yield productivity, average 1000-kernel weight and plant height and earliness were more adapted to moderate than cold environments. In this study the genetic materials were evaluated under two limiting factors (cold and drought) of durum yield production in highland rainfed conditions of Iran. Because of lower mean yield in colder environments, there was clear discrimination between cold-tolerant (old varieties i.e., Zardak and Sardari) and cold-susceptible (i.e., breeding lines) genotypes. Clear discrimination was possible for drought because the trials were conducted under both rainfed and irrigated conditions. Positive increase in yield and yield stability of breeding lines compared to the check cultivars, indicating genetic improvement for both high yield and stability performances in durum wheat breeding program. Most breeding lines originating from the International Center for Agricultural Research in the Dry Areas (ICARDA) gene bank could be considered as a genetic resource for specific adaptation, and yield stability. However, durum breeding in the Mediterranean basin, particularly in Iran, has made little progress in cold regions and most progress was in warm and moderate cold regions, highlighting the difficulty to increase yield of durum wheat under cold conditions. The GGE biplot methodology, as has been shown to be very effective for analyzing GE interaction data, allowed a meaningful and useful summary of GE data and assisted in examining the natural relationships and variations in genotype performance among various testing environments. The finding that some test environments may be better than others for genotype evaluation suggests that the genotypes may be evaluated in fewer but more representative environments while still achieving the same or even better evaluation. Based on GGE biplot analysis, locations with high repeatability were Shirvan with high representativeness, Qamloo with average representativeness and Ilam with zero representativeness. Locations with low repeatability included Kermanshah and Uromieh with average representativeness and Ardabil and Maragheh with negative representativeness. These results verified high GE interaction in some locations (i.e., Ardabil and Maragheh ) compared to others (i.e., Shirvan, Qamloo and Ilam). In conclusion, current durum wheat selection may lead to yield stability and specific adaptation, which provides opportunities for this collection to be useful for genetic improvement of both drought and cold tolerance in durum.