Changes in yield and yield stability of durum wheat genotypes (triticum turgidum ssp. Durum) under different environments and water regimes

Maintaining high grain yield and genotype performance stability under drought stress is a challenging objective for wheat breeders. This study aims to investigate the agronomic performance of six durum wheat genotypes, grown during three cropping seasons (2017, 2018 and 2019) at three locations in Tunisia: Medenine (south, arid climate) and Kairouan (center, semiarid climate) under two irrigation regimes and Kodia (north, sub-humid climate) under rainfed conditions. We analyzed for these genotypes their responsiveness to these environments through yield components at maturity. Results showed that highest grain yield was recorded under rainfed conditions in the sub-humid region with no significant variability between genotypes. The experiments in semiarid and arid areas were carried out as the combinations (site/year) and were denoted as Environments E1 (Kairouan 2017), E2 (Kairouan 2018) and E3 (Medenine 2019). A significant effect of the interaction genotype by environment (G x E) was observed in all environments, this effect was explained by the variability among climatic factors from one environment to another. Results showed that all the genotypes gave their highest yields in E1. The most productive genotype was Khiar followed by ON15 and YT13 as tolerant genotypes. The susceptible ON66 genotype gave the lowest yield in this environment. Using the stress susceptibility percentage index (SSPI(GY)), results showed that ON15 (11%), Maali (23%) and YT13 (27%) seemed to be more tolerant than Khiar (42%), ON58 (48%) and ON66 (63%) in E1. Stability analysis revealed that according to GY stability ranking, Khiar, Maali, YT13 and ON15 are the most stable genotypes. The tolerant genotype YT13 showed the best stable response and the most performing one contrariwise to the susceptible genotype ON66 which showed the worst performance for GY and lowest yield stability. These results lead to conclude that this pair of genotypes (YT13 and ON66) has an interesting contrasting behavior and could be useful for comparative study in understanding drought tolerance mechanisms and for upcoming breeding programs based on adaptability to Tunisian climates.