Diallel analysis of kernel weight and grain-filling traits in maize grown under contrasting nitrogen supply

Understanding the inheritance of maize (Zea mays L.) kernel weight (KW) under contrasting nitrogen (N) supply is crucial for obtaining high KW across diverse N conditions. This work evaluated broad-sense heritability (H-2), general combining ability (GCA), and specific combining ability (SCA) under contrasting N levels for (i) KW and kernel number per plant and (ii) grain-filling traits represented by the duration of lag and effective filling phases, kernel growth and desiccation rates, maximum water content and volume, and moisture content at physiological maturity. A six-parent full diallel cross generated via Griffing's method 3 was tested under high (N200) and low (N0) N supply in 2 years (Y). For the various traits: (i) F-1 hybrid, and F-1 by Y and/or N interactions were significant (p < 0.05); (ii) GCA was significant at both N levels and affected (p < 0.05) by the Y effect; (iii) SCA was important (p < 0.05) only at N200; and (iv) GCA sum of squares was higher than those of SCA (except for KW). For KW and grain-filling traits, H-2 and GCA/SCA ratios were higher at N0 than at N200, suggesting low-N environments would be more advantageous for developing genetic selection. Lag-phase duration (LPD), kernel desiccation rate (KDR), and kernel maximum water content (KWCMAX) had higher H-2 (>= 0.70) and GCA/SCA ratio than KW, particularly under N0. Thus, the highest KW hybrid (LP2xLP662) was composed of inbreds with high GCA for LPD, KDR and KWCMAX, revealing superior KW hybrids could be selected from the GCA of mentioned traits.