Molecular Plant Breeding 2024, Vol.15, No.6, 340-350 http://genbreedpublisher.com/index.php/mpb 346 yield and grain quality due to mycotoxin contamination. These diseases pose a global threat to maize production, necessitating the development of resistant maize varieties. Genetic improvement through the identification of stable quantitative trait loci (QTL) is crucial for enhancing resistance to these diseases and improving selection efficiency in breeding programs (Chen et al., 2016; Akohoue and Miedaner, 2022; Yuan et al., 2022). The breeding program aims to integrate QTL mapping and single nucleotide polymorphism (SNP) markers to develop maize varieties with improved resistance to FER and GER, thereby ensuring higher yield and better grain quality. 8.2 Methodology: QTL mapping and SNP marker integration The methodology involved the use of various populations and advanced genetic techniques to map QTL associated with resistance to FER and GER. For instance, a meta-analysis of 224 QTL identified in 15 studies was conducted using dense genome-wide SNP markers to identify meta-QTL (MQTL) and candidate genes (Akohoue and Miedaner, 2022). Another study utilized a set of 246 diverse inbred lines from the IBM Syn10 DH population to detect QTL associated with GER resistance, combining QTL mapping with GradedPool-Seq (GPS) to identify significant SNPs (Figure 3) (Yuan et al., 2022). Additionally, genome-wide association studies (GWAS) and linkage mapping were employed to detect alleles and validate QTL associated with FER resistance in tropical maize germplasm (Chen et al., 2016). These approaches enabled the identification of genomic regions and candidate genes linked to disease resistance, facilitating the integration of these markers into breeding programs. Figure 3 Phenotypic variation of Gibberella ear rot (GER) severity between the parental lines and the distribution of GER scale at three environments in IBM Syn10 DH populations (Adopted from Yuan et al., 2022) Image caption: A, Phenotypic variation of GER severity in parental lines Mo 17 and B 73 after Fusarium graminearuminoculation in the field. Bar: 2 cm. B, The histograms display correlation and frequency distribution of the GER scale for IBM Syn10 DH populations at three independent environments and the best linear unbiased prediction; the scatterplots and the numbers display the pairwise scatter plot and pairwise correlation coefficient, as determined by the paired t test; the red curve shows the fitted model. ** indicates a significance level at P< 0.01 (Adopted from Yuan et al., 2022) 8.3 Outcomes: improved disease resistance and yield in maize varieties The integration of QTL mapping and SNP markers has led to significant advancements in breeding maize varieties with enhanced resistance to FER and GER. For example, the meta-analysis identified 40 MQTL, with 29 associated with multiple FER- and GER-related traits, and 14 MQTL harboring 2 272 candidate genes (Akohoue
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