Molecular Plant Breeding 2024, Vol.15, No.4, 198-208 http://genbreedpublisher.com/index.php/mpb 203 Figure 3 Characterization and application of the salinity-induced osmotic stress (SIOS)-tolerant sulfotransferase ZmSOT alleles in maize (Zeamays ssp. mays) (Adopted from Liang et al., 2021) Image caption: (a–f) The molecular marker for the SIOS-tolerant ZmSOT alleles. The green lines indicate the variants likely associated with the functional variations of ZmCS3 (a), ZmCYP709B2 (b) and ZmUGT (c). The red arrows in (a)–(c) indicate the location of the InDels that have been used to develop the PCR-based marker for the favorable alleles of ZmCS3(d), ZmCYP709B2(e) and ZmUGT (f). (g–i), The appearances (g) and leaf water contents (WCs) (h–i) of the control and salt-treated maize plants (genotypes as indicated). Data in (h) and (i) are means ± SD of three independent experiments. Statistical significance was determined by one-way ANOVA test. Bars, 5 cm (g) (Adopted from Liang et al., 2021) 5.4 Nutritional quality enhancement Enhancing the nutritional quality of maize has been another significant contribution of exotic varieties. The integration of advanced breeding techniques and genetic tools has facilitated the improvement of nutritional traits in maize. For example, the development of maize cultivars with enhanced nitrogen-use efficiency not only improves yield but also contributes to better nutritional quality by optimizing nutrient uptake and utilization (Liu et al., 2019). Additionally, the focus on breeding for nutritional limitations, such as improving nitrogen-use efficiency, has been a key objective in modern crop breeding programs (Benavente et al., 2021). In summary, the contributions of exotic maize varieties to agronomic traits are multifaceted, encompassing yield improvement, abiotic and biotic stress tolerance, and nutritional quality enhancement. These advancements have been driven by a combination of genetic discoveries, advanced breeding techniques, and collaborative efforts across various institutions and regions. 6 Case Studies 6.1 Successful incorporation of exotic traits in commercial hybrids The integration of exotic germplasm into commercial maize hybrids has shown significant promise in enhancing yield potential and stability. For instance, the study by Nyoni et al. (2023) demonstrated that incorporating exotic genes, particularly from temperate regions, into sub-tropical maize germplasm resulted in hybrids with higher grain yield and stability across diverse agro-ecologies. One notable hybrid, G44, exhibited a grain yield of 10.52 t/ha and matured earlier than the best commercial check hybrid, highlighting the potential benefits of exotic germplasm in improving local maize varieties.
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