## 4 Discussion  
The goal of every breeder is to obtain new varieties with the most favorable traits. For many years, attempts have been made through crossbreeding to obtain genotypes that would have higher yields and greater disease resistance than their parental forms. However, this is a very time-consuming and, unfortunately, inefficient process [67; 68; 69; 70; 71]. Selection and choosing individuals for mating is an important stage of breeding work. Some of the oldest and most common criteria determining selection of forms for further mating are phenotypic traits. Using the effects of general and specific combinatorial ability can lead to improved accuracy in predicting grain yield performance of hybrids. This accuracy can be improved by using the best linear unbiased prediction methods which are a promising tool for hybrid breeding programs [72]. Testing based on phenotypic traits can be subject to error due to the dependence of the expression of these traits on environmental conditions [73]. Diversity and population structure can vary significantly between morphological traits and molecular markers. Elucidating such discrepancies is crucial for further progress in breeding, as well as for maintaining genetic resources [49; 50; 51]. In order to achieve better breeding results, classical selection is increasingly being supplemented with test results using molecular markers linked to performance traits. Molecular markers based on DNA analysis are independent of environmental factors and show a high degree of polymorphism. The development of molecular techniques has revolutionized many areas of life and science. High-throughput genotyping and sequencing technologies make it possible to create predictive models that estimate the genetic value of the entire genotyped population. In a pre-breeding program, predictions speed up reproducible selection using rapid cycles in greenhouses by skipping some of the phenotyping steps [74]. The development of molecular techniques and genomics has allowed for a more complete understanding of the genetic basis of functional traits and thus the introduction of more informative techniques. The use of molecular markers in crop breeding is now a very convenient diagnostic tool in selection of favorable genotypes (MAS) [75]. Molecular markers assist breeding work during selection of an introduced gene or in selection of a genetic background. The most important advantages of MAS include the fact that selection of breeding material is primarily independent of the developmental stage of the plants under study and external factors [76; 77]. Molecular markers appear to be a promising tool in predicting heterosis in various species, for example, in canola [78], maize [79; 80], oats [81], rice [82], and wheat [14; 83]. \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Significant Effect of** & **The Number of** & **Phenotypic Distance** & **Genetic Distance** \\ \cline{1-2}
**Heterosis** & **Significant Effects** & **Phenotypic Distance** & **Genetic Distance** \\ \hline Positive & 68 & 0.190 (0.120) & 0.326 (0.007) \\ Negative & 46 & 0.305 (0.039) & \(-0.426\) (0.003) \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Pearson linear correlation coefficients and \(p\)-values (in brackets) between phenotypic distances (Mahalanobis) and genetic distances and heterosis effects calculated when genetic distances were greater than 0.6 and heterosis effects were statistically significant. Physical mapping and association mapping make it possible to identify/select markers linked to genes determining quantitative traits, including the most important for breeders--yield [84, 85]. The use of molecular markers in research has provided more accurate information about the non-allelic gene interaction--epistasis--which is so unfavorable during the selection process [6, 86, 87, 88, 89, 90].