Bioscience Methods 2024, Vol.15, No.6, 255-263 http://bioscipublisher.com/index.php/bm 258 Field trials conducted as part of the CSM approach demonstrated statistically significant yield gains of up to 5.8% in some selected sublines. These trials were highly replicated and spanned multiple environments and years, ensuring robust validation of the yield improvements (Sebastian et al., 2010). Additionally, another study involving 944 RILs from a diallel cross of early-maturing varieties identified major QTLs that significantly contributed to seed yield, further validating the effectiveness of MAS in yield improvement (Zhu et al., 2021). The economic and agricultural benefits of using MAS for developing high-yielding soybean varieties are substantial. By enabling the early and precise selection of superior genotypes, MAS reduces the time and cost associated with traditional breeding methods. The improved yield performance of MAS-selected varieties translates to higher productivity and profitability for farmers. Moreover, the integration of MAS with conventional breeding can accelerate the development of varieties with enhanced yield and other desirable traits, contributing to food security and sustainable agriculture (Sebastian et al., 2010; Zhu et al., 2021). 4 Impact of MAS on Disease Resistance in Soybean 4.1 Major diseases affecting soybean production Soybean cyst nematode (SCN), caused by Heterodera glycines, is one of the most destructive pests affecting soybean production globally. The integration of genetic analysis, molecular biology, and genomic approaches has significantly enhanced our understanding of the genetic control of SCN resistance. Major resistance loci such as Rhg1 and Rhg4 have been cloned, and novel resistance quantitative trait loci (QTL) have been discovered, leading to the development of gene-specific DNA markers useful for marker-assisted selection (MAS) (Figure 2) (Kim et al., 2016; Kadam et al., 2016). Figure 2 Phylogenetic tree of the Rhg1 locus constructed on the basis of 5 451 haplotypes using 19 652 accessions and the SoySNP50K (Adopted from Kadam et al., 2016) Image caption: Green diamond shaped bullets showthe high copies of the Rhg1 allele present in the known soybean lines from maturity groups III to V; pink diamond shaped bullets show the low copies of the Rhg1 allele present in the known soybean lines from maturity groups III to V; and light blue hexagon shaped bullets showing the resistant lines (Adopted from Kadam et al., 2016) Phytophthora root rot (PRR), caused by Phytophthora sojae, is another significant disease limiting soybean yield. Resistance to PRR is complex and involves both major resistance genes (Rps) and QTL for partial resistance. Recent advancements in genetic mapping and sequencing have identified several Rps genes and QTL, facilitating the development of diagnostic markers and MAS strategies for breeding PRR-resistant soybean cultivars (Zhong et al., 2017; Jiang et al., 2020; Karhoff et al., 2022; Chandra et al., 2022).
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