Performance of Rainfed Bread and Durum Wheat Cultivars Under Different Tillage Options in Wheat-Based Dryland Cropping Systems

The expansion of conservation agriculture (CA) requires an immediate attention on targeted breeding for the next generation of wheat cultivars that are adapted to CA system and maintain their productivity under severe drought conditions in unpredictable Mediterranean environments. In this study, eight released bread and durum wheat cultivars, differing in growth habit, were evaluated for grain yield and 15 agro-physiological traits under both conventional tillage (CT) and conservation agriculture (CA) systems using split-plot arrangements in randomized complete blocks design with three replications, in three cropping seasons (2017–2020) under rainfed conditions, at Sararood field station, Kermanshah, Iran. Cultivar, year and tillage-system main effects were significant (P < 0.01) and accounted for 1.5%, 57.8%, and 10.5% of the total variation in grain yield, respectively. The wheat cultivars performed better in conventional than conservation agriculture system with grain yield superiority varied from 4 to 35%, depending on amount and distribution pattern of precipitation over crop seasons. The best performing cultivar in conservation agriculture system was cv. Baran, winter bread wheat, while the best performing cultivar under conventional tillage was cv. Rijaw, facultative bread wheat. Cv. Sadra had the highest grain yield stability followed closely by cv. Rijaw. The positive relationships observed between grain yield and important agro-physiological traits, suggesting the efficiency of indirect selection of traits for improving grain yield under the two different tillage systems. The trait profile of wheat cultivars was strongly affected by year, depending on growth habit, and varied from one system to another. In conclusion, positive interaction of genotype and traits under two systems indicated that some traits (i.e., number of spike/m−2, SPAD reading, normalized difference vegetative index (NDVI), days to heading, 1000-kernel weight and grain filling duration) were effective in genotype adaptation to a particular system. Based on the findings, the distribution pattern of precipitation during cropping season was among the major determinant factor in success of rainfed wheat productivity. The wheat genotypes also significantly interacted with different tillage systems, implying the need for specific adaptation to tillage systems and environments.