Genetic correlation
The results presented in Table 2 indicate the values of genetic correlation coefficients between total seed yield and its yield components. There was a positive and highly significant correlation between total seed yield and the number of pods per plant, the number of seeds per pod and the 1000-seed weight, with coefficients of 0.731**, 0.819** and 0.956**, respectively. Additionally, a positive and highly significant correlation was observed between 100-seed weight and both the number of pods per plant and the number of seeds per pod, with coefficients of 0.712** and 0.852**, respectively. Moreover, there was a positive and highly significant correlation between the number of seeds per pod and the number of pods per plant, which amounted to 0.796**.
These findings are consistent with those reported by
Mehra et al. (2020),
Dutta et al., (2021), Verma et al., (2021), Alizawee et al. (2025) and
Mahmood et al. (2025),
Khomphet, (2025). The reason for this strong correlation between seed yield and its components can be attributed to the effects of genetic factors as well as the influence of nano-phosphorus fertilization.
Genetic and environmental variances, heritability and phenotypic and genotypic coefficients of variation
The data presented in Table 3 indicated that the genetic variance components are greater than the environmental variance components for all traits studied, which confirmed the importance of genetic components in the emergence of these traits. Such high genetic variation is due to the association between genetic factors and environmental factors (in this case, nano-phosphorus fertilization treatment). The estimates of genetic variation for yield and its components (seeds per pod, number of pods per plant, weight of 100 seeds and seed yield) were 0.01962, 1278.167, 1.577477 and 41073.86, respectively (
Al-Jubouri et al., 2024;
Hindi et al., 2025). This made clear that the genetic stability is high due to the genes responsible for controlling these characters, which in turn caused high broad sense heritability estimates for the studied traits.
The values of environmental variance were 0.00043748, 7.04524, 0.05323167 and 3740.471, respectively, whereas phenotypic variance values for traits were 0.020058, 1285.212, 1.630709 and 44814.33, respectively. Broad-sense heritability percentages for traits were 97.81%, 99.45%, 96.73% and 91.65%, respectively (
Kuswantoro, 2019;
Al-Mafarji et al., 2024). The high broad-sense heritability percentages for traits suggest that those traits are determined
Apart from this, the phenotypic coefficient of variation was greater than the genotypic coefficient of variation and their values were 6.985425, 44.23141, 11.59175 and 8.699609, respectively, against genotypic coefficients of variation of 6.908825, 44.11001, 11.40098 and 8.328639, respectively. The above findings have been supported by
Dutta et al., (2021) and
Verma et al., (2021). The phenotypic and genetic variance values were particularly high for grain yield, which positively influenced the high broad-sense heritability estimate of 91.65% for this trait, indicating that the environmental influence was relatively limited compared to the genetic effect. This agrees with the conclusions reported by
Sharif et al., (2024b), Dutta et al., (2021), Verma et al., (2021) and
Mehra et al., (2020).
Accordingly, the traits of the number of branches per plant and the number of pods per plant showed high genotypic coefficients of variation, suggesting greater opportunities for successful selection for these traits, reflecting the substantial genetic variation present among them.
GGE-biplot stability analysis
The stability of the studied cultivars was tested across environments represented by different levels of nano-phosphorus fertilizer (0, 1000, 2000, 3000, 4000 and 5000 ppm), labeled as E1, E2, E3, E4, E5 and E6, respectively, using the GGE-Biplot technique to study the genotype × environment interaction. Fig 1 shows the relationship among the studied environments, where environments E3 and E5 were identified as the most desirable, having the highest PC1 values and the lowest PC2 values. An environment is considered ideal when it has a high capacity to discriminate among cultivars (high PC1) and is representative of all tested environments (PC2 close to zero)
Habtegebriel and Abebe, (2023). Environments E3 and E5 contributed to increased grain yield, unlike environments E4, E2 and E1. PC1 accounted for 79.8% of the total variation, emphasizing the effect of environments on cultivar performance, whereas PC2 accounted for 16.1% of the total variation. The cultivars above zero on the positive axis of PC1 were favorably affected towards high grain yield, whereas near zero on the positive axis of PC2 were less productive. Cultivar G4 was observed to be the most productive cultivar.
The relationship between the preferred cultivars for different environments is depicted in Fig 2. Cultivar G4 preferred environments E3 and E5, as environments E3 and E5, as well as cultivar G4, were in the same quarter of the biplot diagram defined by similar scores of PC1 and PC2. The best-suited environment for cultivar G4 would be E4, showing genetic stability of the cultivar across different environments.
Fig 3 above illustrates the stability of a cultivar using the Average Environment Coordination (AEC) technique developed by
Habtegebriel and Abebe, (2023). This graph is marked by two distinct lines. The first line marked by a red color passes through the origin, known as the average environment axis, where it reflects high trait expression in the direction of the arrowhead. Cultivar G4 contributed more towards yield, as well as mean performance. The other line, marked blue, is the stability axis, where arrows in both ends point perpendicular to the average environment axis. Cultivars close to the average environment axis contributed towards high stability, while those farther away contributed towards low stability. G4 contributed towards high stability, followed by G2, which contributed towards low stability.
Fig 4 above shows the relationships between the studied cultivars. The grain yield was highest in environments E3, E5 and other environments in cultivar G4, while the other environments have relatively low stability. The rays that originate from the origin indicate environmental vectors, which show the extent to which environments are correlated to each other. The cosine value between any pair of environmental vectors shows how environments are correlated, while the length of the vectors shows how environments can discriminate stable genotypes. The longer the vector, the better it can discriminate stable genotypes. The performance of the other environments was also observed, where those with longer projections performed above average, while those with shorter projections performed at or around average levels. The grain yield was highest in G4, while that of G2 was lowest.
Fig 5 identifies the ideal genotype across the studied environments. An ideal genotype combines high yield with high stability and suitability across diverse environments. The farther the positive PC1 values from the origin, the higher the yield and stability of the genotype, while longer PC2 vectors indicate lower yield and stability. The biplot analysis showed that cultivar G4 was the ideal genotype, combining high yield and stability, positioned in the first group represented by a concentric circle in the biplot. The second group included cultivar G3, which was closest to the ideal genotype.
Fig 6 shows the relationship among studied environments The most ideal environment will be characterized by high ability to distinguish among cultivars (high PC1) and will be well representative (close to PC2=0) (
Habtegebriel and Abebe, (2023;
Singamsetti et al., 2024). Environments E3 and E5 were deemed to be the most ideal environments, performing well on grain yield among all cultivars, followed by E1 that was similar in terms of grain yield, but E4 was the worst on grain yields among all cultivars. Cultivar G4 was most consistent across the four environments, outyielding all on grain yield. The most ideal environments were E3 and E5, while the least ideal were E2 and E4, which were farthest from the center of the concentric circles. The influence of environments on cultivars was well demonstrated using the PC1 and PC2 axes, establishing that G4 was the most ideal genotype.
The result from the GGE-Biplot showed efficiency in the search for the most stable genotypes over the environment and in the interpretation of the relationships among genotypes and the environment. These results agree with the findings from
Ikeogu and Nwofia (2013),
Carvalho et al., (2021), Al-Abody et al. (2019) and
Obua et al., (2024), which showed that this method is effective in the search for stable genotypes and optimal environments.
Hierarchical clustering analysis
Hierarchical cluster analysis was conducted based on the yield characters and their components for the varieties to establish their genetic similarity or divergence depending on their reaction to environmental factors (concentrations of nano-phosphorus fertilizer). This procedure is based on the measure of the distance showing the degree of divergence and the grouping based on performance and genetic make-up of the varieties. Genetic similarity between the varieties was established based on the degree of their genetic proximity as shown in Table 4 and Fig 7 showing the genetic similarity (difference) between the studied varieties.
The data showed that the genetic distance between the crops Iman and Shaima was 248.270, indicating that they have a close genetic relation, possibly because they possess similar genetic materials, meaning that crops from different origins may not always have large genetic distances. The fact that Iman and Shaima have a close genetic relation may be because they possess identical desirable genes, which would be valuable in breeding. This means that among the two crops that have a close genetic relation, one can replace the other in situations where one is lost, while breeding among them should not take place.
On the other hand, the highest genetic distance was noticed between Taqa-2 and Lee-74 cultivars (68233.667), representing the existence of a high degree of divergent genetic structures that could be effectively utilized through hybridization programs and subsequent selection to obtain superior cultivars adapted to the environmental conditions of this study. This statistical method could be considered an efficient and alternative method to biotechniques whenever the latter are unavailable or unattainable. The hierarchical clustering method was effective in interpreting genetic relationships effectively to represent complex interactions of studied cultivars and enables comparison of them easily. Therefore, this supports genotypes with maximal genetic similarity or differences in addition to managing genetic resources effectively. The findings of this study are consistent with
Khalil et al., (2020), Ragade et al., (2024), Chiemeke et al., (2024) and
Al-Asadi and Al-Abody (2025), since all mentioned that this method was quite efficient to differentiate genetically divergent genotypes effectively.