Molecular Plant Breeding 2025, Vol.16, No.2, 146-155 http://genbreedpublisher.com/index.php/mpb 148 germplasm, such as temperate and tropical sources, has been shown to improve yield performance and stability in sub-tropical breeding programs, further highlighting the benefits of utilizing diverse genetic resources (Nyoni et al., 2023). 3.2 Germplasm innovation for disease resistance traits Identifying and incorporating new disease-resistant genes into maize breeding programs is crucial for developing resilient cultivars. The use of doubled haploid technology has significantly accelerated the process of developing pure lines with desired traits, including disease resistance. This technology allows for the rapid fixation of traits and the unlocking of genetic variation, making it a valuable tool in modern maize breeding (Dwivedi et al., 2015; Meng et al., 2021). For example, the REGNUR project has focused on identifying and increasing access to disease-resistant germplasm in eastern and southern Africa. Through diallel analysis, the project has evaluated the combining ability of elite inbred lines for grain yield and resistance to multiple diseases, enabling the pyramiding of resistance genes in new cultivars (Vivek et al., 2010). This approach has led to the development of hybrids with enhanced resistance to several diseases, demonstrating the effectiveness of germplasm innovation in improving disease resistance traits. 3.3 Successful cases of germplasm innovation in maize disease-resistant breeding Several successful cases of germplasm innovation have significantly enhanced disease resistance in maize breeding. The CIMMYT, in collaboration with public and private sector institutions, has developed and deployed elite tropical maize germplasm with tolerance to key abiotic and biotic stresses, including diseases (Figure 1). This has resulted in the release of stress-tolerant maize cultivars across sub-Saharan Africa, Asia, and Latin America, showcasing the impact of multi-institutional efforts in germplasm innovation (Prasanna et al., 2021). Figure 1 Phenotypic comparison of maize hybrids developed by CIMMYT-Mexico under different stress conditions (Adopted from Prasanna et al., 2021) Image caption: A: Phenotypic comparison under controlled drought stress, showing leaf yellowing and plant wilting; B: Phenotypic comparison under controlled heat stress, illustrating the growth response of different maize hybrids to heat stress; C: Phenotypic comparison under controlled waterlogging stress, with some plants exhibiting stunted growth or leaf yellowing due to excess water (Adopted from Prasanna et al., 2021)
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