Tree Genetics and Molecular Breeding 2025, Vol.15, No.1, 18-24 http://genbreedpublisher.com/index.php/tgmb 21 breeders to introduce more superior traits and limits the ability of kiwifruit to adapt to different environmental changes (Hanley, 2018). Sekhon et al. (2019) indicated that insufficient genetic diversity makes kiwifruit more prone to diseases. Bacterial canker disease caused by Pseudomonas syringae pv. actinidiae has already had a significant impact on many kiwifruit-growing areas. 5.2 Limitations in germplasm collection and preservation Ferguson’s early research, that is, in 2007, found that institutions such as HortResearch Kiwifruit Germplasm Resource Bank had collected a considerable amount of genetic resources, but it was still quite difficult to actually apply these wild resources to breeding. Hu et al. (2022) hold that environmental changes and the destruction of the growth environment of wild species put many precious genetic resources at risk of loss. The genetic structure of kiwifruit is relatively complex (such as its high heterozygosity and polyploid characteristics), which makes the genetic analysis and breeding process more troublesome and hinders the utilization of diversity (Wang et al., 2022). Sekhon et al.’s research in 2019 demonstrated that the prevalence of Psa, a bacterial disease, has exacerbated this issue, posing a threat to the survival of many important genotypes in the germplasm bank. 5.3 Challenges in integrating diverse traits into elite cultivars The characteristics of kiwifruit, such as dioecious plants, long juvenile period and climbing growth pattern, all make the breeding process more complicated (Hanley, 2018). Zhang et al. (2015) argued that even with high-density genetic maps and the identification of gender-related genetic markers, it is still very difficult to truly integrate good traits. Li et al. (2014) indicated that the genetic background of kiwifruit is very complex, and many are polyploids, requiring special breeding methods such as hybridization between polyploids. There are many difficulties in the practical operation of technologies such as SNP genotyping chips and genomic selection to stably incorporate complex traits into commercial varieties. 6 Opportunities for Future Kiwifruit Breeding 6.1 Leveraging advanced genomic tools for diversity exploration Modern omics technologies such as genomics, proteomics and metabolomics have changed the understanding of kiwifruit biology and made breeding more targeted (Zhang et al., 2015; Nazir et al., 2024). Breeders can use these techniques to conduct more in-depth research on the genetic diversity of the Actinidia genus and integrate useful traits into new varieties. Methods such as MAS, GS, and CRISPR-Cas9 gene editing are useful for precisely improving traits and are important tools for cultivating excellent kiwifruit varieties. High-density SNP genotyping chips, GBS and other technologies can better locate useful genes, support QTL analysis and promote the rapid breeding of high-quality varieties (Figure 2) (Oh et al., 2018; Shu et al., 2023). 6.2 Building international collaborations for germplasm exchange Sharing the genetic resources of kiwifruit in various regions is crucial for developing new varieties that adapt to different environments (Ferguson, 2007; Nazir et al., 2024). Cooperation enables researchers to collect, evaluate and utilize germplasm resources more comprehensively and ensure access to genetic materials from more diverse sources. Li et al. (2014) and Hu et al. (2022) also found that international cooperation is beneficial for introducing good traits such as enhanced disease resistance and stress tolerance of wild species into breeding programs and improving the overall performance of new varieties. 6.3 Expanding breeding targets to address climate change and market demands Future breeding projects must take into account issues such as extreme weather and disease pressure. Bacterial canker disease (Psa) is a very serious threat that requires specialized disease-resistant varieties to deal with (Sekhon et al., 2019). Consumers’ demands for taste, nutrition and appearance are also getting higher and higher. New varieties should also improve in these aspects. Early research by Gea (2011) indicates that the combination of traditional breeding methods and modern genomic technology enables breeders to produce kiwifruit varieties that can withstand environmental pressure and meet market preferences more quickly, making the entire industry more sustainable and competitive.
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