1 Introduction

Sweet potato (Ipomoea batatas L.) is a vital food crop globally, ranking as the sixth most important food crop worldwide. Originating from America, sweet potatoes have become a staple in many countries due to their rich nutritional profile and versatility in various culinary applications (Lee et al., 2019). This crop is particularly valued for its high content of sugars, slowly digestible/resistant starch, vitamins, minerals, and bioactive compounds such as carotenoids and polyphenols, which contribute to its health benefits, including the prevention of certain cancers and cardiovascular diseases. The global market for sweet potatoes is substantial, with China leading in production, reflecting the crop's significant economic and nutritional impact (Escobar-Puentes et al., 2022; Istri et al., 2023).

In China, sweet potato breeding is of paramount importance due to the country's leading role in global production and the crop's contribution to food security and economic stability. The diverse phenotypic and genotypic traits of domesticated sweet potato varieties in China allow for the development of cultivars that are tailored to specific environmental conditions and consumer preferences. This genetic diversity is crucial for enhancing yield, disease resistance, and nutritional quality (Shen et al., 2019). For instance, studies have shown significant genetic variability among sweet potato genotypes, which can be harnessed to improve resistance to diseases such as sweet potato viral disease (SPVD) and to optimize yield under various climatic conditions (Lamaro et al., 2022). This breeding effort is essential for sustaining the crop's productivity and meeting the nutritional needs of the population (Swanckaert et al., 2021).

The study aims to explore the genetic resources available for sweet potato breeding in China and  evaluate their utilization in developing improved sweet potato varieties. Specifically, the study aims to assess the genetic diversity of sweet potato cultivars in China and identify key phenotypic and genotypic traits that contribute to yield, disease resistance, and nutritional quality. Additionally, the study evaluates the performance of various sweet potato genotypes under different environmental conditions. It also provides recommendations for breeding strategies that can enhance the productivity and resilience of sweet potato crops in China. By achieving these objectives, the study seeks to contribute to the sustainable development of sweet potato breeding programs in China, ensuring the crop's continued role in food security and economic development.

2 Genetic Resources for Sweet Potato Breeding

2.1 Types of genetic resources available

Landraces and traditional cultivars are crucial genetic resources for sweet potato breeding in China. These varieties have been cultivated over long periods and are well-adapted to local environmental conditions. They often possess unique traits such as disease resistance, drought tolerance, and specific taste or nutritional qualities. For instance, the study on Kam Sweet Rice highlights the importance of landraces in maintaining genetic diversity and unique traits that are  absent in modern cultivars (Liu et al., 2022). Similarly, sweet potato landraces can provide a rich source of genetic variation that is essential for breeding programs aimed at improving crop resilience and productivity.

Wild relatives of sweet potatoes are another valuable genetic resource. These plants often contain genes that confer resistance to pests, diseases, and environmental stresses, which can be introgressed into cultivated varieties. The importance of wild relatives is underscored by research on potato genetic diversity, where wild relatives contributed new and unique alleles to the gene pool, enhancing genetic diversity and breeding potential (Wang et al., 2019). Utilizing wild relatives in sweet potato breeding can similarly introduce beneficial traits that are not present in cultivated varieties. Modern breeding lines and hybrids represent the forefront of sweet potato breeding efforts. These lines are developed through systematic breeding programs that combine desirable traits from various genetic resources. The study on plant breeding history emphasizes the role of modern breeding techniques in developing high-yielding, disease-resistant cultivars (Bradshaw, 2017). In sweet potato breeding, modern lines and hybrids can be used to rapidly incorporate beneficial traits from landraces and wild relatives, leading to the development of superior cultivars.

2.2 National and international gene banks

National and international gene banks play a critical role in the conservation and utilization of sweet potato genetic resources. These institutions collect, preserve, and provide access to a wide range of genetic materials, including landraces, wild relatives, and modern breeding lines. The research on potato genetic diversity in China highlights the importance of gene banks in maintaining a diverse genepool for future breeding programs (Wang et al., 2019). Similarly, gene banks for sweet potatoes ensure that valuable genetic resources are available for breeding efforts aimed at improving crop resilience and productivity (Bethke et al., 2017).

2.3 Challenges in genetic resource collection and preservation

Despite the importance of genetic resources, there are several challenges in their collection and preservation. One major challenge is the loss of genetic diversity due to the replacement of traditional cultivars with modern high-yielding varieties, as noted in the study on plant breeding history (Bradshaw, 2017; Guan et al., 2021). Additionally, the natural habitats of many wild relatives are threatened by environmental changes and human activities, which complicated in situ conservation difficult. Ex situ conservation in gene banks also faces challenges such as maintaining the viability and genetic integrity of stored materials over long periods. Addressing these challenges requires coordinated efforts to document, conserve, and utilize genetic resources effectively, ensuring their availability for future breeding programs (Hao et al., 2020).

3 Sweet Potato Breeding Programs in China

3.1 Overview of breeding objectives

The primary objective of sweet potato breeding programs in China is to enhance both yield and quality. This involves selecting varieties that not only produce higher yields but also possess desirable traits such as improved taste, texture, and nutritional content. For instance, the development of transgenic sweet potatoes has shown promise in increasing yield and nutritional value, with varieties like 'Xushu 18' and 'Kokei' demonstrating enhanced resistance to pests and environmental stresses, thereby contributing to higher productivity (Imbo et al., 2016).

Stress tolerance is a critical focus area of breeding, especially in response to challenges such as drought, salinity, and pests. Breeding programs aim to develop varieties that can withstand these stresses to ensure stable production. For example, transgenic sweet potato lines expressing genes such as cry8Db and cry7A1 have shown reduced weevil infestation, while those expressing the oryzacystatin-1 (OC1) gene have demonstrated enhanced resistance to nematodes and viruses (Imbo et al., 2016). Additionally, the study of drought tolerance mechanisms and the identification of drought-tolerant genotypes are essential for breeding programs targeting regions prone to water scarcity (Laurie et al., 2022; Sapakhova et al., 2023).

Nutritional enhancement and biofortification are increasingly important objectives. Breeding efforts are focused on increasing the content of essential micronutrients, such as iron, zinc, and vitamins, in sweet potato varieties. For instance, orange-fleshed sweet potato cultivars like Bophelo have been identified for their superior nutritional content, including higher levels of Fe, Zn, and dietary fiber, which are crucial for addressing malnutrition (Laurie et al., 2022). Biofortification through both conventional breeding and genetic engineering is being pursued to develop varieties with enhanced nutritional profiles (Diepenbrock and Gore, 2015; Garg et al., 2018; Medina-Lozano and Díaz, 2022).

3.2 Key Institutions Involved in Breeding Efforts

Several key institutions are at the forefront of sweet potato breeding in China. These include the Chinese Academy of Agricultural Sciences (CAAS), which leads research and development in crop improvement, including sweet potato breeding. The International Potato Center (CIP) collaborates with Chinese institutions to enhance sweet potato varieties for better yield, stress tolerance, and nutritional value. Local Agricultural Research Institutes also play a significant role by conducting region-specific breeding programs to address local agricultural challenges and improve sweet potato production.

3.3 Advances in breeding techniques

Conventional breeding methods remain a cornerstone of sweet potato improvement. These methods involve selecting parent plants with desirable traits and cross-breeding them to produce offspring with enhanced characteristics. This approach has been instrumental in developing high-yielding and stress-tolerant varieties (Obidiegwu et al., 2015; Tiwari et al., 2022). Molecular breeding and marker-assisted selection (MAS) have revolutionized sweet potato breeding by enabling the precise identification and incorporation of beneficial traits. Techniques such as genomic selection and the use of molecular markers linked to stress tolerance and nutritional traits have accelerated the development of improved varieties (Lau et al., 2018; Medina-Lozano and Díaz, 2022).

Genomic selection and CRISPR/Cas genome editing are cutting-edge technologies being applied in sweet potato breeding. Genomic selection involves using genome-wide markers to predict the performance of breeding lines, thereby speeding up the selection process. CRISPR/Cas technology allows for precise editing of the sweet potato genome to introduce or enhance specific traits, such as drought tolerance and pest resistance (Imbo et al., 2016; Lau et al., 2018). These advanced techniques hold great promise for the future of sweet potato breeding, enabling the development of varieties that can meet the growing demands for food security and nutritional quality.

4 Utilization of Genetic Resources in Sweet Potato Breeding

4.1 Strategies for genetic diversity utilization

The utilization of genetic diversity is crucial for improving sweet potato breeding programs. Genetic diversity provides a pool of traits that can be harnessed to enhance crop resilience, yield, and nutritional quality. In sweet potato breeding, strategies to utilize genetic diversity include the assessment of population structure and genetic diversity using molecular markers (Zhu et al., 2024). For instance, a study on sweet potato accessions in China used 62,363 SNPs to evaluate genetic diversity, revealing significant within-group diversity and identifying a core germplasm set that can be used for future breeding efforts (Figure 1) (Su et al., 2017). This approach ensures a broad genetic base and is essential for the long-term sustainability of the breeding programs.

Figure 1 Location of the sweet potato accessions from around the world, highlighting China (Adopted from Su et al., 2017)

4.2 Crossbreeding and hybridization efforts

Crossbreeding and hybridization are fundamental techniques in sweet potato breeding aimed at combining desirable traits from different parent lines. These methods have been employed to improve various traits such as starch quality and disease resistance. For example, crossbreeding efforts in potatoes have shown that hybridization can create wider genetic variation than the parent lines, leading to the selection of progenies with improved starch properties (Ahmed et al., 2019). Similarly, hybridization in sweet potatoes can be used to combine traits such as high yield, disease resistance, and improved nutritional content, thereby enhancing the overall performance of new cultivars (Zhang et al., 2021).

4.3 Role of biotechnology in genetic resource use

Biotechnology plays a pivotal role in the utilization of genetic resources for sweet potato breeding. Techniques such as genome-wide assessment and molecular marker analysis facilitate the identification of valuable genetic traits and their incorporation into breeding programs. The use of specific length amplified fragment (SLAF) sequencing in sweet potato has enabled a detailed analysis of genetic diversity and the development of a core germplasm set, which serves as a valuable resource for breeding (Su et al., 2017). Additionally, molecular tools have been instrumental in identifying genes that control important traits, thereby accelerating the breeding process and improving the precision of trait selection (Machida-Hirano, 2015).

4.4 Integration of wild relatives into breeding programs

The integration of wild relatives into sweet potato breeding programs is a strategy to introduce new genetic variations and desirable traits that are not present in cultivated varieties. Wild relatives often possess traits such as disease resistance, drought tolerance, and improved nutritional content, which can be beneficial for breeding programs. The genetic diversity present in wild relatives of potato, for example, has been successfully utilized to enhance the genetic base of cultivated varieties (Machida-Hirano, 2015; Pandey et al., 2021). By incorporating wild relatives into sweet potato breeding programs, breeders can tap into a wider genetic pool, thereby improving the adaptability and resilience of new cultivars to various environmental stresses.

In conclusion, the effective utilization of genetic resources in sweet potato breeding involves a combination of strategies, including the assessment of genetic diversity, crossbreeding, the application of biotechnology, and the integration of wild relatives. These approaches collectively contribute to the development of improved sweet potato varieties that meet the demands of food security, nutrition, and sustainable agriculture (Ojwang' et al., 2023).

5 Case Study: Application of Local Genetic Resources in a Regional Breeding Program

5.1 Background and selection of genetic materials

Sweet potato (Ipomoea batatas (L.) Lam.) is a crucial crop in China, playing a significant role in  food security and agricultural sustainability. The selection of genetic materials for breeding programs is pivotal to enhancing crop yield, disease resistance, and adaptability to various environmental conditions. Recent studies have highlighted the genetic diversity and population structure of sweet potato accessions in China, which are essential for effective breeding strategies. For instance, a genome-wide assessment using specific length amplified fragment (SLAF) sequencing identified three major genetic groups among 197 sweet potato accessions, providing a valuable resource for breeding programs (Su et al., 2017). Additionally, retrotransposon-based insertion polymorphism (RBIP) markers have been utilized to analyze the genetic diversity of sweet potato germplasm, revealing significant intergroup genetic variation (Meng et al., 2021).

5.2 Breeding process and methodology

The selection of parental lines is based on their genetic diversity and desirable traits. Studies have shown that sweet potato accessions in China exhibit considerable genetic variability, which can be harnessed for breeding purposes. For example, the use of RBIP markers has facilitated the identification of genetically diverse parental lines, which are crucial for creating hybrids with improved traits (Meng et al., 2021). Hybridization involves crossing selected parental lines to combine their desirable traits, such as high yield, disease resistance, and environmental adaptability.

Field trials are conducted to evaluate the performance of hybrid progenies under different environmental conditions. Traits such as yield, disease resistance, and stress tolerance are assessed. The evaluation process involves phenotypic and genotypic analyses to ensure the selection of superior hybrids. For instance, phenotypic evaluation and molecular biotechnology have been employed to assess the genetic diversity and trait performance of sweet potato cultivars, providing insights into their adaptability and potential for improvement (Hu et al., 2022).

Multi-environment testing is essential to determine the stability and adaptability of new sweet potato hybrids across different regions. This involves testing the hybrids in various agro-ecological zones to evaluate their performance under diverse environmental conditions. Genetic diversity studies have shown that sweet potato accessions exhibit varying levels of adaptability, which can be leveraged to develop region-specific cultivars (Su et al., 2017; Meng et al., 2021).

5.3 Challenges encountered and solutions implemented

Several challenges are encountered in the breeding process, including biotic stresses such as diseases and pests, and abiotic stresses like drought and poor soil conditions. Recent research has focused on understanding the mechanisms of resistance to biotic stress in sweet potato, identifying stress-related genes, and employing genetic engineering to enhance resistance (Figure 2) (Yang et al., 2023). Additionally, the genetic variability of sweet potato viruses poses a significant challenge, necessitating comprehensive studies to identify and control viral diseases (Wang et al., 2021).

Figure 2 The mechanism of resistance to Fusarium wilt in sweet potato (Adopted from Yang et al., 2023)

5.4 Outcomes and impact on local agriculture

The application of local genetic resources in sweet potato breeding has led to the development of new cultivars with improved yield, disease resistance, and environmental adaptability. These advancements have had a positive impact on local agriculture by enhancing food security and providing farmers with resilient crop varieties. The development of a core germplasm set for sweet potato has also facilitated future breeding efforts, ensuring the continuous improvement of sweet potato cultivars (Su et al., 2017).

5.5 Lessons learned and recommendations for future breeding

The case study emphasizes the importance of utilizing genetic diversity and advanced molecular techniques in sweet potato breeding. Future breeding programs should focus on expanding the genetic base by incorporating diverse germplasm resources and employing modern biotechnological tools for precise trait selection and improvement. Conducting extensive multi-environment testing is essential to ensure the adaptability and stability of new cultivars. Additionally, addressing biotic and abiotic stresses through integrated pest management and genetic engineering approaches will be crucial. By implementing these strategies, future breeding programs can develop superior sweet potato cultivars that meet the growing demands of both local and global agriculture (Vargas et al., 2020).

6 Challenges and Opportunities in Genetic Resource Utilization

6.1 Limitations in genetic resource access and use

One of the primary challenges in the utilization of genetic resources for sweet potato breeding in China is the limited access to diverse germplasm. This limitation is often due to administrative and legal barriers that restrict the exchange of genetic materials across national borders. Public breeders face significant hurdles in obtaining the necessary genetic diversity to enhance their breeding programs, which is crucial for developing climate-resilient crops (Galluzzi et al., 2020). Additionally, the lack of appropriate technologies to exploit germplasm sets, such as crop wild relatives and landraces, further exacerbates this issue.

6.2 Intellectual property and germplasm exchange policies

Intellectual property rights and germplasm exchange policies present another significant challenge. International agreements like the Convention on Biological Diversity (CBD) and the Nagoya Protocol have recognized the sovereign rights of countries over their genetic resources, leading to more restrictive and cumbersome access to plant genetic resources (PGR) (Ebert et al., 2023). Although the International Treaty on Plant Genetic Resources for Food and Agriculture (ITPGRFA) attempted to ease this situation by establishing a globally harmonized multilateral system, it remains limited to only a few crops. This restriction hampers the continuous and easy access to genetic diversity, which is essential for breeding new, resilient varieties.

6.3 Opportunities from climate-resilient breeding

Despite these challenges, there are significant opportunities in breeding sweet potatoes that are resilient to climate change. The development of drought-tolerant varieties is particularly crucial, as osmotic stress negatively impacts the productivity of sweet potato cultivation. By employing physiological, metabolic, and genetic modifications, breeders can select and improve genotypes that are better adapted to drought conditions. This approach not only enhances food security but also supports smallholder farmers by making the creation of drought-resistant varieties more cost-effective (Sapakhova et al., 2023).

6.4 Prospects for Collaboration with Global Breeding Programs

Collaborating with global breeding programs offers promising prospects for overcoming some of the challenges in genetic resource utilization. Integrating genomic selection (GS) and emerging technologies, such as high-throughput genotyping, phenotyping, and gene editing, can accelerate the development of cultivars with improved yields and enhanced resistance to biotic and abiotic stresses (He and Li, 2020). Furthermore, increased sharing of genetic resources, genomic data, and bioinformatics expertise between developed and developing economies can help meet the challenges posed by climate change and the growing demand for food. Such collaborations can also facilitate the exchange of best practices and innovative breeding techniques, ultimately contributing to the global effort to enhance crop resilience and productivity. By addressing these challenges and leveraging the opportunities, the utilization of genetic resources for sweet potato breeding in China can be significantly improved, leading to more resilient and productive crop varieties (Cooper and Messina, 2022).

7 Future Directions for Sweet Potato Breeding in China

7.1 Expanding the genetic base for breeding

To enhance the genetic diversity of sweet potato breeding programs in China, it is crucial to incorporate a wide range of genetic resources. This includes local landraces, wild relatives, and elite lines from international breeding programs. By broadening the genetic base, breeders can introduce new traits that improve yield, disease resistance, and nutritional quality. For instance, studies on potatoes have shown that incorporating diverse genotypes can lead to the discovery of unique alleles that are beneficial for breeding (Wang et al., 2019). Similar strategies can be applied to sweet potatoes to ensure a robust and resilient breeding program.

7.2 Leveraging advances in genomics and biotechnology

The integration of modern genomics and biotechnological tools can significantly accelerate sweet potato breeding efforts. Techniques such as CRISPR/Cas9 and TALENs have been successfully used in other crops like potato to enhance nutritional content and remove anti-nutritional compounds (Hameed et al., 2018). These technologies can be employed to develop transgene-free sweet potato varieties with improved traits. Additionally, the availability of sweet potato genome sequences can facilitate marker-assisted selection and genomic selection, making the breeding process more precise and efficient.

7.3 Strengthening breeding-research partnerships

Collaborative efforts between breeding programs and research institutions are essential for the continuous improvement of sweet potato varieties. Partnerships with international organizations like the International Potato Center (CIP) can provide access to advanced breeding techniques and genetic resources (Ojwang' et al., 2023). Moreover, multidisciplinary workshops and the use of tools like the G+ tools can help evaluate and enhance the gender-responsiveness of breeding programs, ensuring that the developed varieties meet the needs of all stakeholders (Swanckaert et al., 2021).

7.4 Addressing consumer preferences and market needs

Future sweet potato breeding programs in China should be increasingly demand-driven, focusing on consumer preferences and market needs. This involves developing varieties that not only have high yield and disease resistance but also meet the nutritional and culinary preferences of consumers. For example, breeding strategies that target market segments with high rates of malnutrition and vitamin deficiencies can have a significant impact on public health (Ojwang' et al., 2023). Additionally, understanding and addressing consumer preferences can help overcome challenges related to the commercialization of new varieties, ensuring that they are well-received in the market. By focusing on these future directions, sweet potato breeding programs in China can achieve greater success in developing varieties that are not only high-yielding and resilient but also meet the nutritional and market demands of the population (Lebot, 2020; Markel and Shih, 2021).

8 Concluding Remarks

The utilization of genetic resources in sweet potato breeding in China has shown significant potential in addressing both agronomic and environmental challenges. Key findings from the reviewed studies highlight the importance of genetic diversity and phenotypic variability in crop improvement. For instance, the study on cultivated potatoes in China demonstrated a high level of genetic variation, which is crucial for breeding programs aimed at improving crop traits such as tuber starch content and growth period. Similarly, sweet potato has been identified as a critical crop for food security, especially under conditions of global climate change. The physiological and biochemical adaptations of sweet potato to drought stress are essential for developing drought-tolerant varieties. Additionally, the genetic divergence among sweet potato genotypes for silage production underscores the potential for selecting and breeding high-performance varieties.

To maximize the benefits of genetic resource utilization in sweet potato breeding, several policy and research recommendations are proposed. Enhanced funding for genetic research is essential, with increased investment needed to develop high-yielding, stress-tolerant sweet potato varieties. This includes support for both traditional breeding methods and modern biotechnological approaches. The development of genomic resources is also critical. Establishing comprehensive genomic databases for sweet potato, including genome sequencing, trait mapping, and the use of genomics-assisted breeding techniques, can facilitate more efficient breeding programs. Climate-resilient breeding programs should be a priority, focusing on the development of sweet potato varieties with superior drought tolerance and other stress resistance traits. These efforts are crucial for sustainable agriculture in the face of climate change. Finally, collaboration and knowledge sharing among research institutions, government agencies, and farmers are essential. This collaborative approach can enhance the exchange of knowledge and resources, thereby accelerating the development and adoption of improved sweet potato varieties.

The role of genetic resource utilization in sustainable agriculture cannot be overstated. By leveraging genetic diversity and advanced breeding techniques, it is possible to develop sweet potato varieties that are not only high-yielding but also resilient to environmental stresses. This is particularly important in the context of global climate change, where the demand for food security and sustainable agricultural practices is ever-increasing. The integration of traditional breeding methods with modern genomic technologies offers a promising pathway to achieve these goals. Ultimately, the successful utilization of genetic resources in sweet potato breeding will contribute significantly to sustainable agriculture and food security in China and beyond.

Acknowledgments

We express our heartfelt gratitude to the two anonymous reviewers for their valuable comments on the manuscript.

Funding

This reserach received funding from the Ningbo Public Welfare Research Technology Project (2024S014).

Conflict of Interest Disclosure

The authors affirm that this research was conducted without any commercial or financial relationships that could be construed as a potential conflict of interest.

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