Molecular Pathogens 2024, Vol.15, No.3, 106-118 http://microbescipublisher.com/index.php/mp 109 Figure 2 Scheme of marker-assisted selection (MAS) and identification of quantitative trait loci (QTLs) involved in wheat disease resistance (Adopted from Jabran et al., 2023) Image caption: 1: Biparental mapping population development, i.e., F2 plants, NILs, RILs, BILs, etc., segregating for disease resistance. 2: Precise phenotyping for resistance scaling to a specific pathogen. 3: Genomic DNA isolation from selected plants. 4-6: Evaluation of genome-wide distributed polymorphic DNA markers and construction of linkage maps. 7, 8: Statistical modeling of linkage groups using phenotypic-genotypic data followed by mapping of resistance-associated QTLs (Adopted from Jabran et al., 2023) Another advantage is the precision and accuracy of trait selection. Traditional breeding relies on phenotypic selection, which can be influenced by environmental factors and may not always accurately reflect the plant's genetic potential. Molecular markers and genomic tools provide a more reliable means of selecting for specific traits, reducing the risk of selecting undesirable characteristics (Miedaner and Korzun, 2021; Jabran et al., 2023). Molecular breeding also enables the combination of multiple resistance genes into a single cultivar, enhancing the durability of disease resistance. For example, the use of gene pyramiding, where multiple resistance genes are combined, has been shown to provide more robust and long-lasting resistance to diseases like rust and Fusarium head blight in wheat (Maré et al., 2020; Luo et al., 2021). This approach is particularly important in combating evolving pathogens that can quickly overcome single-gene resistance (Maré et al., 2020; Luo et al., 2021). 3.3 Challenges and limitations Despite its many advantages, molecular breeding faces several challenges and limitations. One of the main challenges is the complexity of the plant genome and the polygenic nature of many important traits. Identifying and manipulating multiple genes that contribute to a single trait can be difficult and time-consuming (Miedaner and Korzun, 2021; Jabran et al., 2023). Additionally, the interactions between different genes and their combined effect on the phenotype are not always well understood, complicating the breeding process (Lowe et al., 2011). Another limitation is the cost and technical expertise required for molecular breeding. Advanced techniques like genome sequencing and gene editing are expensive and require specialized equipment and knowledge. This can be a barrier for smaller breeding programs or those in developing countries with limited resources (Miedaner and Korzun, 2021; Mapuranga et al., 2022).
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