article · Plants
Evaluating maize hybrids under varied planting densities helps identify varieties capable of delivering higher yields in intensive farming systems. Twenty-eight white maize hybrids derived from eight diverse inbred lines were evaluated across three planting densities at two locations. Increasing planting density reduced chlorophyll content, leaf angle, and individual plant yield, but raised overall grain yield per hectare along with plant height and the interval between anthesis and silking. While both additive and non-additive gene effects influenced all traits, additive gene action proved predominant for most traits. Specific inbred lines showed strong general combining ability for yield, and two hybrid combinations, namely L2 crossed with L5 and L2 crossed with L8, performed well under dense planting. Although molecular genetic distance did not predict hybrid performance or specific combining ability, specific combining ability effectively predicted hybrid performance across densities.
Maximising crop yield per unit of land is essential for improving food security. High-density planting offers an effective path to higher production, but requires maize varieties bred to tolerate crowded conditions without stalling development. Identifying specific parental lines and hybrids adapted to high plant densities provides plant breeders with the genetic resources needed to develop productive varieties for modern agricultural systems.
The findings directly benefit commercial seed companies and public maize breeding programmes aiming to release high-density tolerant varieties. Two specific hybrid crosses, L2 with L5 and L2 with L8, are identified as ready for further verification and promotional testing. The work represents an applied research stage, where candidate hybrids must undergo wider multi-location trials and regulatory evaluation before reaching seed distributors and commercial farmers.
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Knowledge of combining ability and genetic diversity are important prerequisites for the development of outstanding hybrids that are tolerant to high plant density. This work was carried out to assess general combining ability (GCA) and specific combining ability (SCA), identify promising hybrids, estimate genetic diversity among the inbred lines and correlate genetic distance to hybrid performance and SCA across different plant densities. A total of 28 F<sub>1</sub> hybrids obtained by crossing eight adverse inbred lines (four local and four exotic) were evaluated under three plant densities 59,500 (D1), 71,400 (D2) and 83,300 (D3) plants ha<sup>-1</sup> using spilt plot design with three replications at two locations during 2018 season. Increasing plant density from D1 to D3 significantly decreased leaf angle (LANG), chlorophyll content (CHLC), all ear characteristics and grain yield per plant (GYPP). Contrarily, days to silking (DTS), anthesis-silking interval (ASI), plant height (PLHT), ear height (EHT), and grain yield per hectare (GYPH) were significantly increased. Both additive and non-additive gene actions were involved in the inheritance of all the evaluated traits, but additive gene action was predominant for most traits. Inbred lines L<sub>1</sub>, L<sub>2</sub>, and L<sub>5</sub> were the best general combiners for increasing grain yield and other desirable traits across research environments. Two hybrids L<sub>2</sub> × L<sub>5</sub> and L<sub>2</sub> × L<sub>8</sub> were found to be good specific combiners for ASI, LANG, GYPP and GYPH. Furthermore, these hybrids are ideal for further testing and promotion for commercialization under high plant density. Genetic distance (GD) among pairs of inbred lines ranged from 0.31 to 0.78, with an average of 0.61. Clustering based on molecular GD has effectively grouped the inbred lines according to their origin. No significant correlation was found between GD and both hybrid performance and SCA for grain yield and other traits and proved to be of no predictive value. Nevertheless, SCA could be used to predict the hybrid performance across all plant densities. Overall, this work presents useful information regarding the inheritance of maize grain yield and other important traits under high plant density.
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DOI: 10.3390/plants9091140
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