New selection index generation mean analysis of three maize hybrids

In the present study, generation mean analysis was employed to examine the gene effects and inheritance of the Maize Canopy Level Index (MCL i ) in filial generations (P 1 , P 2 , F 1 , F 2 , BCP 1 , and BCP 2 ) of three maize hybrids (Kn 561, Kn 570A, Kn 572) from the portfolio of the Maize Research Institute – Knezha, as part of a broader multi-year investigation (2023-2025). The index represents the ratio between the number of leaves above the upper ear and the number of tassel branches. Since the number of leaves above the ear is a relatively constant trait, a higher index value is determined by a reduced number of tassel branches, which is a trend observed in modern maize hybrids. The results for hybrid Kn 561 indicate moderate gene effects with high heritability of the trait, both in the broad sense (H 2 =0.89) and the narrow sense (h 2 =0.73). For hybrid Kn 570A, a balanced additive (A) and dominance (D) effects were observed, with a pronounced additive-dominance (AD) epistatic interaction. Heritability was moderate in both senses (H 2 =0.44 and h 2 =0.47). The third hybrid, Kn 572, exhibited the highest additive effects (А=0.199), as well as the strongest expression of epistatic effects (AA = 0.334; AD = 0.247). The heritability of the trait in both the narrow and broad sense was the highest among the three hybrids (h² = 0.99; H² = 0.96). From a breeding perspective, hybrid Kn 572 is the most promising regarding the studied trait, as it demonstrated the greatest genetic progress both in the maternal line (P 1 ) and in the hybrid itself (F 1 ). The newly developed index, specific to maize, is easily applicable and can be used both directly and in tandem with other assessments, which contributes to accelerating the breeding process in this crop.