Maize Genomics and Genetics 2024, Vol.15, No.3, 136-146 http://cropscipublisher.com/index.php/mgg 140 identification of landraces with high yield potential and desirable secondary traits under heat stress conditions is crucial for developing heat-tolerant maize varieties (Nelimor et al., 2019). Figure 2 Inflation depicted by Q-Q plots of observed versus expected -log10 (P values) plots for NCLB using the naïve association model (G-test), GLM (G + Q) and MLM (G + Q + K); G = genotype (fixed), Q = ten principal components (fixed), K = kinship matrix (random) for (a) CAAM panel (b) DTMA panel and (c) IMAS panel; Highly significant SNPs identified from MLM model using Manhattan plot (d), plotted with the individual SNPs on the X-axis and − log10 P value of each SNP on the Y-axis for the three panels, CAAM, IMAS and DTMA. The horizontal line shows the cut off P value and the vertical lines represent the common haplotypes identified in haplotype regression analysis across different panels for NCLB resistance (Adopted from Rashid et al., 2020) Image caption: Figure 2 shows the Quantile-Quantile (QQ) plots and Manhattan plots for NCLB resistance association analysis using different models (G-test, GLM, and MLM). The QQ plots illustrate the effects of different models on correcting for genome structure and kinship, with the MLM model displaying the smallest genomic inflation, indicating its high efficiency in NCLB resistance association analysis. The Manhattan plots demonstrate the significant SNP loci identified in the MLM model, highlighting their distribution across the genome and their association with NCLB resistance. These loci provide crucial genetic targets for further molecular breeding and marker-assisted selection, offering valuable insights into the study of maize genetic diversity and its application in disease resistance improvement (Adopted from Rashid et al., 2020) 4.3 Nutritional and quality improvement 4.3.1 Provitamin A biofortification Biofortification of maize with provitamin A is an important strategy to address vitamin A deficiency in populations that rely heavily on maize as a staple food. Genetic approaches to enhance provitamin A content in maize involve the identification and incorporation of favorable alleles associated with increased carotenoid levels. This strategy has shown success in developing maize varieties with significantly higher provitamin A content, contributing to improved nutritional quality (Wen et al., 2011). 4.3.2 Quality protein maize Quality Protein Maize (QPM) is enriched with essential amino acids, particularly lysine and tryptophan, which are deficient in conventional maize. Breeding for QPM involves the incorporation of the Opaque-2 (O2) gene and associated modifiers that improve kernel texture and nutritional quality. The development of QPM varieties has been a significant achievement in enhancing the protein quality of maize, benefiting populations with maize-based diets (Wen et al., 2011).
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