Yield stability analysis in durum wheat: Progress over the last two decades in Italy

Durum wheat ( Triticum durum Desf.) is the main cereal crop in Italy, mostly cultivated in Southern and Central regions. Improving grain yield has been the primary objective of most national breeding programs until the end of the’ 70s. The objective of this study was to evaluate durum wheat yield stability improvements achieved in Italy over twenty years through the national breeding programs. Data from 10 coordinated field trials carried out over two 3-year periods (1977–79 and 1996–98) were considered. Analysis of the mean yield, linear regression coefficients ( b ), coefficients of variability (CV), coefficients of determination ( r 2 ) and deviations from the regression ( S 2 d) allowed us to identify, for each period considered, remarkable differences among different cultivars in terms of yield and yield stability. The stability analysis clearly identified, during 1977–79, two different subgroups of genotypes. The first ( b <1) included cultivars registered in the National Durum Wheat collection before 1974 (Cappelli, Capeiti 8, Trinakria. Appulo, Isa 1), having high adaptability to low-input environments. In contrast, the second subgroup ( b >1) included semidwarf cultivars such as Valnova, Valgerardo, Creso and Valfiora, highly sensitive to environmental variability and pronounced responsiveness to high-input environments. In 1996–1998 yield stability became a primary target. Therefore the national breeding programs promoted comparative trials over-time and over-space. All cultivars selected in those years had b values close to 1 and their mean yield was significantly higher compared to the 1977–79 cultivars. As a result, the most recent cultivars possess both high adaptability traits (typical of those tall cultivars selected in arid and semiarid regions before the 70s) and high yield potential, a trait associated with Rht alleles (Creso and “Val” cultivars)