Maize Genomics and Genetics 2025, Vol.16, No.1, 34-44 http://cropscipublisher.com/index.php/mgg 36 2.3 Global distribution and diversity of germplasm resources The global distribution and diversity of fresh corn germplasm resources are extensive, with significant variations observed across different regions. For example, in China, fresh sweet-waxy corn is cultivated in various provinces such as Inner Mongolia, Jilin, and Heilongjiang, each exhibiting distinct nutritional profiles and fatty acid compositions (Li et al., 2022a; Li et al., 2022b). This regional diversity is crucial for breeding programs as it provides a wide genetic base for selecting superior traits. The genetic variability among different endosperm mutations and genetic backgrounds further enhances the potential for developing fresh corn varieties with improved eating quality and agronomic performance (Azanza et al., 2004). The continuous exploration and evaluation of these germplasm resources are essential for advancing fresh corn breeding and meeting the diverse needs of global markets. 3 Exploration of New Fresh Corn Germplasm Resources 3.1 Traditional sources of germplasm resources Landrace corn varieties are a crucial source of genetic diversity, having been cultivated and adapted over centuries to specific local conditions. For instance, maize landraces from the Aosta Valley in Italy exhibit significant genetic variability and differentiation due to their long-term reproductive isolation and adaptation to mountainous regions (Lezzi et al., 2023). Similarly, landraces from the Emilia Romagna region in Italy have been preserved by farmers in marginal areas, maintaining a rich genetic reservoir that can be utilized for breeding more resilient varieties (Stagnati et al., 2021). In Brazil, the characterization of 25 maize landraces revealed promising genetic potential for breeding, with some landraces showing grain yields comparable to commercial hybrids (Araújo and Nass, 2002). Wild relatives of maize, such as teosinte, offer valuable genetic traits that can be harnessed for modern agriculture. Teosinte, the wild ancestor of maize, has been found to possess higher protein content and unique zein protein profiles compared to modern inbred lines and landraces, indicating its potential for improving kernel traits and grain quality (Flint-Garcia et al., 2009). The genetic diversity present in teosinte and other wild relatives can provide insights into target traits and allelic variants that are beneficial for crop improvement. 3.2 Modern methods for germplasm exploration Molecular markers, such as simple sequence repeats (SSRs), are widely used to assess genetic diversity in maize germplasm. For example, the evaluation of maize landraces from southwest China using 42 SSR loci revealed a high level of genetic diversity, with 246 alleles detected among the landraces (Chen et al., 2016). Similarly, genetic characterization of local maize accessions from the Emilia Romagna region using SSR markers identified 62 different alleles, highlighting the genetic variability among the landraces (Stagnati et al., 2021). These analyses are essential for identifying unique genetic resources that can be utilized in breeding programs. Genomic technologies, such as genome-wide association studies (GWAS) and resequencing, have revolutionized the exploration of maize germplasm. For instance, the mapping of haplotype-trait associations in doubled-haploid lines derived from maize landraces has uncovered beneficial haplotypes for early development traits, which can be integrated into elite germplasm for crop improvement. Additionally, the use of high-density SNP genotyping has facilitated the identification of untapped beneficial variation in landraces, providing new opportunities for breeding programs (Mayer et al., 2020). 3.3 International collaboration in germplasm sharing and conservation International collaboration plays a vital role in the sharing and conservation of maize germplasm. Organizations like CIMMYT have been instrumental in providing improved maize breeding material for non-temperate regions, ensuring the preservation and utilization of diverse genetic resources (Warburton et al., 2008; Hou et al., 2024). Collaborative efforts are also essential for the conservation of traditional maize agrobiodiversity, as seen in the case of Mexican landraces, where strategies have been developed to safeguard rare genotypes and promote in situ conservation (Hayano-Kanashiro et al., 2017). These initiatives are crucial for maintaining the genetic diversity necessary for future crop improvement and resilience against environmental challenges.
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