Analysis of variance for genotypes
Analysis of variance showed significant differences among genotypes for grain yield and maturity duration (Table 2). Its significance has also been reported by
(Edukondalu et al., 2017) and (
Akanksha and Jaiswal, 2019). Therefore, notable variations in rice grain yield and maturity duration among genotypes prove they are appropriate for additional genetic research.
Genetic components of variation
Gene interaction
The regression coefficient values of b (Wr, Vr) for grain yield and maturity duration of rice are 0,69 and 1,08. They are not significantly different from one another (Table 3). It is in line with the findings from the previous research
(Singh et al., 2021) for grain yield and maturity duration. The regression coefficient value of b (Wr, Vr) can be used to determine the gene interaction of a trait. According to the t-test, gene interaction is indicated by the value of b (Wr, Vr), which is statistically different from one another, whereas the value of b, which is non-significantly different, shows that there is no gene interaction (Wr, Vr) from one another. This indicates no interactions among the genes in this research for rice maturity duration and grain yield. This means that each gene cannot affect the other, and no interaction exists between genes that control grain yield and maturity duration.
Gene distribution in the parents
Using H
2 levels, we can ascertain the genes distribution. According to the findings, there was a substantial difference in the H
2 values for rice grain yield and maturity duration (Table 3). This indicates that the genes determining grain yield and maturity inheritance are not evenly distributed among the parents. Table 3 shows that the values of H
1 are 219,78 and 326,51, while the values of H
2 are 223,10 and 257,30 for grain yield and maturity of rice. It was also reported by (
Sharma and Jaiswal, 2021).
The present analysis showed that the values of H
2/4H
1 for grain yield and maturity are 0,25 and 0,19 (Table 3).
Dominance level
The dominance effect can be seen from the value of the mean degree of dominance as estimated by (H
1/D)
1/2. If the value of (H
1/D)
1/2 is more than 1, it indicates over-dominance. If the value of (H
1/D)
1/2 between 0 and 1, it indicates partial dominance (
Hayman, 1954). Table 3 shows that the value of (H
1/D)
1/2 of grain yield and rice maturity is more than 1, which is 1,69 and 2,22. It proves that there is over-dominance in these traits. It is similar to
Rohman et al., (2019) for grain yield.
Dominance effect
The h
2 value indicates the dominance effect. Table 3 shows that the h
2 value significantly differs for grain yield and maturity duration. It was detected during the days from physiological maturity and grain yield, as reported by (
El-Satar, 2017).
Environmental variance
Table 3 shows that environmental variance significantly influenced grain yield but did not considerably influence the maturity duration. This proved that the environment has no significant influence on grain yield and maturity expression.
Raihan et al., (2024) has the identical finding that grain yield per plant and maturity duration for environment was nonsignificant.
Proportion of dominant gene to recessive gene
The Kd/Kr ratio and the F component indicate the ratio of dominant to recessive genes. There are significantly more dominant genes than recessive genes in the parent, as indicated by the positive value of the F component (
Mohammed, 2020). The results showed a positive value of the F component. The ratio of Kd/Kr of the grain yield and maturity of rice is 0,99 and 2,44. The grain yield is 0,99, smaller than one, but maturity is 2,44, which is more than one, as shown in Table 3. It indicates that genes in the parent for grain yield and maturity duration of rice are more dominant.
Number of gene groups
The component of h
2/H
2 indicates the number of gene groups that control a trait. The h
2/H
2 values of grain yield are 1,14 and maturity is 1,24. Both are higher than one. It proves the involvement of many genes, or one gene group responsible for their genetic control. As a result, grain yield and maturity are controlled by many groups of genes. A different result was found by
Kumar et al., (2022) for grain yield and maturity duration.
Direction and order of dominance
A positive value is obtained the correlation of (Wr + Vr) and Yr for rice grain yield and maturity traits (Table 4). M70D is the closest to zero, which means that this parent has the most dominant genes for grain yield. However, the maturity duration is far from zero. It means that the parents have recessive genes. Therefore, the maturity duration in rice is controlled by recessive genes
(Agung et al., 2017).
Heritability
The estimation of broad-sense heritability (h
2bs) for grain yield per plant and rice maturity duration are similar to 56,12 % and 99,05%. Whereas, the estimation of narrow-sense heritability (h
2ns) for these traits are 0,29% and 67,29%. It is identical to the result that is reported by
(Edukondalu et al., 2017) and
(Datta et al., 2024) of a high heritability of grain yield and maturity duration.
Heritability is important in quantitative genetics, particularly selective breeding
(Salam et al., 2016). The estimated value of broad-sense heritability indicates the relative contribution of genetic factors to the variation of the observed trait
(Saha et al., 2019). Grain yield per plant also were had high heritability reported by
(Riyanto et al., 2021).
Combining ability estimation of grain yield and maturity duration
The estimated effect of GCA regarded as an important indicator of the potential parental genotypes for generating superior-breeding populations. Furthermore, the GCA of the parental lines reveals the average performance of a parent in a series of crosses. The significance of GCA effects in two directions in each character revealed that the parents could transfer the high and low values for a trait. However, increasing and decreasing the value of parental characters would be considered as positive and negative GCA effects. Based on their variation, plant breeders desire to produce high-yielding hybrids with better characteristics than the parents. In plant breeding experiments, diallel analysis is beneficial for estimating GCA and SCA
(Yadav et al., 2021). Meanwhile, analysis of combining ability provides an important method for selecting preferred parents and providing the requested information to the nature of gene action which regulates desired traits (
Aamer and Ibrahim, 2020).
Guimarães et al. (2023) found that the general combining ability (GCA) and the specific combining ability (SCA) were significant. Greater contribution of the SCA, compared to GCA, for the variation among crosses, indicates that non-additive effects were more prevalent for the traits evaluated. The same results were reported by
(Dianga et al., 2020) for significant differences of GCA and SCA.
This study demonstrates that general combining ability (GCA) does not significantly affect grain yield, whereas specific combining ability (SCA) does have a significant impact. Conversely, both GCA and SCA significantly influence the maturity duration of rice. The GCA:SCA ratios for grain yield and maturity are greater than one, specifically 1.011 and 9.23 (Table 5), indicating that additive gene action is more predominant than nonadditive gene action in the expression of these traits.