Genetic Analysis of Some Yield Components in Single Hybrids of Yellow Maize (Zea mays L.)
Abstract
A half-diallel cross among six maize inbred lines was carried out in 2023 at the Maize Research Department, General Authority for Scientific Agricultural Research. In 2024, fifteen hybrids, the control variety Ghouta 82, and the parental lines were evaluated to estimate general and specific combining ability and heterosis for ear height, ear length, ear diameter, and number of rows per ear. Significant differences were observed among lines and hybrids for all traits. The hybrid (P6 × P4) exceeded Ghouta 82 in ear height, while all hybrids surpassed it in ear length, ear diameter, and number of rows per ear. Except for (P5 × P2), all hybrids showed positive heterosis, and nine exhibited significant heterosis compared to the best parent in row number. Ear height was mainly controlled by additive gene effects, while both additive and nonadditive effects influenced the remaining traits, with additive effects predominating.
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Introduction
Maize (Zea mays L.) belongs to the Poaceae family, tribe Maydeae. It is a monoecious, annual herbaceous plant (Hallauer and Miranda, 1981). Maize is grown in a wide temperature range between 50°N and 40°S, and from sea level to an altitude of 3,300 m (Saeed and Saleem, 2000). Yellow corn constitutes approximately 75% of the feed provided to poultry in Syria. With the growth of the livestock sector and the poultry industry, demand for corn has increased, and the gap between need and local production has widened (Alexander, 2003), reaching 89% (Statistical Abstract, 2006). Since production capacity is linked to genetic makeup and its responsiveness to growth factors, local production of yellow corn can be increased through the optimal application of agricultural practices (soil preparation, planting date, seed rate, and fertilizer formulas), postplanting maintenance (irrigation, weeding, etc.), and through supporting modern breeding programs that work to develop new, high-yielding genetic materials, especially single crosses.
Crop yield is the most important agricultural trait (Zdunic et al., 2008). It is a complex quantitative trait whose inheritance is controlled by a large number of major and minor genes (Hassan, 1991). It cannot be directly improved, especially when dealing with a cross-pollinated crop such as maize. Therefore, to overcome this problem, the yield trait is studied through its components. The mechanism of its inheritance is investigated, and the nature of the genetic action that can achieve an increase in yield is determined. This information can be used in planning breeding programs (Melchinger et al., 1986) by identifying the traits suitable for indirect selection for yield, and choosing the appropriate selection method (Mohammadia et al., 2003).
Maize ranks second globally after wheat in terms of cultivated area and first in terms of production. In 2008, the global area cultivated with maize reached approximately 1,071,094 hectares, producing approximately 9,736,434.48 million tons (FAO, 2023). In the Arab world, maize ranks third after wheat and barley in terms of cultivated area and second after wheat in terms of production.
Conclusion
Based on the findings of this study, the following conclusions can be drawn:
4.1 Based on analysis of variance and means:
The inbred lines used in the hybridization process showed highly significant variation, indicating genetic divergence among them. The highly significant variation in the hybrids confirmed the genetic divergence between the parental inbred lines used in the hybridization.
4.2 Based on hybrid means:
The hybrid (P6 × P4) significantly outperformed the registered variety Ghouta 82 in the trait of ear height (desirable lowerear placement). All hybrids outperformed the registered variety Ghouta 82 in the traits of ear length, ear diameter, and number of rows per ear, with the exception of the hybrid (P6 × P3) for ear length.
4.3 Based on heterosis:
All hybrids outperformed the average of both parents and the best parent with positive and highly significant differences for the traits of ear height, ear diameter, and number of rows per ear, except for the hybrid (P5 × P2), which showed nonsignificant heterosis. Meanwhile, nine hybrids showed significant heterosis compared to the best parent for the trait of number of rows per ear.
4.4 Based on general combining ability of inbred lines:
The inbred lines (P4) and (P6) had the best general combining ability for ear height
The inbred lines (P2) and (P5) had good general combining ability for ear length
The inbred lines (P6) and (P3) were the best inbred lines for general combining ability for ear diameter
The lines (P6), (P1), and (P3) had the highest GCA for number of rows per ear
4.5 Based on specific combining ability:
The hybrids (P6 × P5) and (P4 × P1) had beneficial (negative) but non-significant SCA for ear height
The hybrids (P3 × P2) and (P6 × P5) had good SCA for ear length
For ear diameter, the hybrids (P2 × P1), (P5 × P3), and (P5 × P4) had good SCA
The hybrids (P5 × P4), (P2 × P1), and (P6 × P3) had the best SCA for number of rows per ear
4.6 Based on variance components and nature of genetic behavior:
Additive gene effects predominated the inheritance of ear height, as confirmed by the σ²GCA/σ²SCA ratio (7.89), with additive genetic variance (837.69) much greater than dominance variance (53.09). Both additive and non-additive gene effects contributed to the inheritance of ear length, ear diameter, and number of rows per ear. The σ²GCA/σ²SCA ratios (2.30, 2.45, and 1.94, respectively) confirmed the dominance of additive genetic action for these traits, and the degree of dominance values (0.467, 0.452, and 0.507) reinforced this finding.
These findings provide valuable information for hybrid maize breeding programs, identifying superior parental lines and promising hybrid combinations for yield improvement
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