Increasing nitrogen use efficiency in modern agriculture is important for obtaining high yields and reducing production costs and environmental pollution. Globally, price reduction and environmental concerns advocate a lower use of nitrogen (N) fertilizer for wheat (Triticum aestivum L.) crop, especially for wheat hybrids. The objective of this study was to assess combining ability at different N levels for agronomic traits and nitrogen use efficiency (NUE) via diallel analysis in wheat hybrids. Four spring wheat cultivars were used to produce a 4 × 4 full diallel cross with the reciprocals. Parents of various origins and their diallel F2-hybrids were evaluated in field under 0, 120 and 240 kg ha-1 N doses. The results showed that there was much genotypic variance among nitrogen doses for the NUE, grain yield, agronomic and quality traits. Significant genotypic differences in the yield, protein yield, protein content and NUE were identified among hybrids. General combining ability effect of parents for the grain yield and protein content, and specific combining ability effect of hybrids for the NUE and grain yield significantly changed depending on nitrogen levels. Both genetic and reciprocal effects showed interaction with nitrogen doses in determining the NUE of wheat. Because of the reciprocal x N interaction, the hybrids' reciprocal responses to increasing nitrogen levels revealed positive or negative changes in the yield and NUE characteristics. The winner among hybrids was identified for grain yield and grain nitrogen yield (GNY) at the optimum N level according to the GGE biplot analysis. Inqualab91 x Chils was found to be desirable for selecting NUE traits.

27.3.2022