Molecular Plant Breeding 2024, Vol.15, No.3, 132-143 http://genbreedpublisher.com/index.php/mpb 133 information on the advancements and practical applications of MAS, contributing to the development of genetically superior tree varieties that meet economic and ecological demands. 2 Fundamentals of Marker-Assisted Selection 2.1 Definition and principles of MAS Marker-Assisted Selection (MAS) is a modern plant breeding technique that utilizes molecular markers to select plants with desirable traits. This approach is grounded in the principles of genetics, where specific DNA sequences (markers) are associated with particular traits. Unlike traditional breeding methods, which rely on phenotypic selection, MAS allows for the identification of specific genes or genomic regions associated with traits of interest, thereby accelerating the breeding process and increasing its precision. The principles of MAS involve the identification of markers linked to traits, the development of marker-trait associations, and the use of these markers to select plants that carry the desired genetic traits (Boopathi, 2020; Kumawat et al., 2020; Hasan et al., 2021). 2.2 Types of markers used in MAS 2.2.1 Molecular markers Molecular markers are segments of DNA that are associated with a particular location within the genome. They are used to identify genetic differences between individuals. Common types of molecular markers include Simple Sequence Repeats (SSRs), Single Nucleotide Polymorphisms (SNPs), and Sequence Tagged Sites (STS). These markers are highly polymorphic, co-dominant, and reproducible, making them ideal for use in MAS (Hasan et al., 2021; Darmanov et al., 2022). 2.2.2 DNA markers DNA markers are specific sequences within the genome that can be used to identify individuals or species and to associate genetic variation with phenotypic traits. Examples of DNA markers used in MAS include SSRs, SNPs, and Genotyping by Sequencing (GBS). These markers are used to create genetic maps and to identify Quantitative Trait Loci (QTLs) associated with important traits such as disease resistance, yield, and quality (Kumawat et al., 2020; Hasan et al., 2021). 2.3 Advantages of MAS over traditional breeding methods MAS is a powerful tool that leverages molecular and DNA markers to enhance the efficiency, accuracy, and speed of plant breeding programs, offering significant advantages over traditional methods. It significantly reduces the time required to develop new varieties by allowing for the early selection of desirable traits. This is particularly important in tree breeding, where long generation times can slow down the breeding process (Grattapaglia et al., 2018; Moriguchi et al., 2020; Degen and Müller, 2023). MAS increases the accuracy of selection by targeting specific genes or genomic regions, thereby reducing the influence of environmental factors on phenotypic selection (Boopathi, 2020; Hasan et al., 2021). MAS can be used to pyramid multiple genes for complex traits, enhancing the overall genetic gain and improving the efficiency of breeding programs (Osei et al., 2018; Kumawat et al., 2020; Darmanov et al., 2022). MAS is cost-effective in the long run, as it reduces the need for extensive field trials and phenotypic evaluations (Hasan et al., 2021). 3 Breakthroughs in Marker-Assisted Selection 3.1 Technological advances in MAS 3.1.1 High-throughput sequencing High-throughput sequencing technologies have revolutionized the field of marker-assisted selection (MAS) by enabling the rapid and cost-effective sequencing of entire genomes. This advancement has facilitated the identification of numerous single nucleotide polymorphisms (SNPs) and other genetic markers that are crucial for MAS. For instance, the development of high-throughput sequencing has allowed for the precise mapping of quantitative trait loci (QTLs) and the identification of gene families involved in disease resistance in forest trees (Younessi-Hamzekhanlu and Gailing, 2022). Additionally, the integration of high-throughput sequencing with other genomic tools has enhanced the accuracy and efficiency of MAS in various plant breeding programs (Salgotra and Stewart, 2020; Hasan et al., 2021).
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