Tree Genetics and Molecular Breeding 2025, Vol.15, No.2, 70-79 http://genbreedpublisher.com/index.php/tgmb 76 7.3 Challenges faced and how they were overcome Maghdouri et al. (2021) found that after adjusting the cold wet lamination treatment method and improving the composition of the seedling substrate, problems such as low germination rate, uneven growth of seedlings, and incompatibility during grafting could be improved. Germination would be faster and the seedlings would be more uniform. The long juvenile period of kiwifruit and dioecious plants make the breeding cycle longer. The CRISPR/Cas9 technology can enable plants to flower earlier and even form bisexual flowers, accelerating the speed of breeding (Varkonyi-Gasic et al., 2018; 2021) Incompatibility problems are prone to occur when grafting between different species. Li et al. (2021) selected rootstocks and scions with closer genetic relationships and higher binding degrees for combination in order to increase the survival rate and improve the success rate of grafting. 8 Field Performance and Commercialization 8.1 Evaluation of hybrid varieties in field trials Field trails will examine the agronomic traits of plants, such as their growth patterns, flowering times, and resistance to diseases. Varkonyi-Gasic et al. (2018) mutated the CENRORADIALIS-like gene in kiwifruit using CRISPR/Cas9 technology and found that this modification could make the plants more compact and enable earlier flowering, which was beneficial for both breeding and field performance. Iliescu et al. (2022) identified male hybrid varieties with high pollen germination rates, which are crucial during field pollination and can enhance fruit setting rates. 8.2 Fruit yield, quality, and market acceptance Abbate et al. ’s research in 2021 found that artificial pollination is more effective than natural wind or insect pollination, increasing fruit setting rate, fruit weight, fruit diameter and seed quantity, and improving the overall quality of the fruit. Maghdouri et al. (2021) found that improving the layering method of seeds during the seedling stage and combining it with appropriate seedling substrates can make seed germination more uniform, seedlings grow stronger, and lead to higher yields. Wu (2018) developed new kiwifruit varieties with various flesh colors such as green, yellow and red. Different colors make the fruits more attractive and more acceptable to consumers, resulting in better market performance. 8.3 Commercial success stories and economic impact Hanley’s breeding work in New Zealand in 2018 introduced yellow-fleshed and red-fleshed kiwifruits, which were more popular than the traditional green-fleshed varieties and also made the market larger. Wu (2018) indicated that establishing an efficient in vitro culture system enables faster breeding and brings new varieties to the market earlier to meet the demands of consumers. Xie et al. (2019) found that by identifying specific molecular markers, the identity of a variety can be confirmed. This is helpful in resolving legal disputes over varieties, ensuring the authenticity of kiwifruits sold on the market, protecting consumers' rights and interests, and making the market more trustworthy. 9 Challenges and Limitations 9.1 Genetic bottlenecks and breeding constraints Kiwifruit takes a long time to grow from young seedlings to flowering and fruiting, and is dioecious (Hanley, 2018). The complexity of genes, the high degree of heterozygosity and the situation of polyploidy make the breeding of new varieties more troublesome. Maghdouri et al. (2021) found that its seeds contain dormant embryos, which sometimes germinate slowly and irregularly, and the seedlings grow unevenly, affecting the efficiency of seedling raising. Hu et al. (2022) indicated that with significant environmental changes nowadays, the growth areas of some wild kiwifruits have been destroyed, and the genetic diversity within the Actinidia chinensis complex is also at risk. These resources must be well protected to ensure the sustainable development of the kiwifruit industry. 9.2 Environmental and regulatory challenges Extreme weather, bacterial canker disease and other problems have brought great pressure to the cultivation of kiwifruit (Hanley, 2018). These situations are difficult to deal with. If there are regulations on the use of advanced
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