Molecular Plant Breeding 2024, Vol.15, No.6, 379-390 http://genbreedpublisher.com/index.php/mpb 382 4.2 Marker-assisted selection (MAS) and genomic selection (GS) Marker-assisted selection (MAS) and genomic selection (GS) are advanced breeding techniques that utilize molecular markers to accelerate the breeding process. MAS involves the use of DNA markers linked to specific traits of interest, allowing for the selection of plants carrying these markers without the need for extensive phenotypic evaluation. This method has been particularly useful for traits that are difficult to measure or have low heritability (Tiwari et al., 2022; Huang and Hong, 2024). Genomic selection (GS), on the other hand, uses genome-wide marker data to predict the breeding value of individuals. This approach allows for the simultaneous selection of multiple traits, including those controlled by many small-effect genes, which are often challenging to improve through MAS alone. GS has shown promise in increasing the accuracy and efficiency of selection, thereby accelerating genetic gains in breeding programs (Varshney et al., 2017; Merrick et al., 2022; Sandhu et al., 2022). 4.3 Gene editing and biotechnology applications Gene editing and biotechnology applications represent the frontier of modern plant breeding. Techniques such as CRISPR/Cas9 allow for precise modifications of the plant genome, enabling the introduction, deletion, or alteration of specific genes. This technology offers the potential to develop sweet potato varieties with enhanced traits such as disease resistance, improved nutritional content, and better adaptability to environmental stresses (Nahirñak et al., 2022). Biotechnological methods also include genetic transformation techniques, such as Agrobacterium-mediated transformation and particle bombardment, which have been widely used in other crops like potatoes. These methods allow for the introduction of new genes into the plant genome, providing opportunities to enhance traits that are difficult to achieve through conventional breeding (Nahirñak et al., 2022). The integration of these advanced biotechnological tools with traditional breeding methods holds great promise for the future of sweet potato improvement. 5 Case Studies in Sweet Potato Breeding 5.1 Case study: establishing a sweet potato resistance identification nursery To address the challenge of sweet potato basal rot in high-risk areas, the Wenzhou Academy of Agricultural Sciences in Zhejiang of China established a resistance identification nursery in a key region heavily affected by sweet potato blight. The primary goal was to identify and promote blight-resistant sweet potato varieties to combat the devastating impact of the disease and improve crop yield and sustainability in the region. The institute collected approximately approximately 350 breeding materials and 110 sweet potato germplasm resources (Table 1; Figure 2) for resistance identification from across the country. Field evaluations were conducted, focusing on agronomic traits and resistance to root rot (a critical disease for sweet potatoes). Ultimately, over 10 superior sweet potato resources were selected, including CH60, CP37, CP158, CJ3056, and QX3009, all of which demonstrated excellent disease resistance with infection rates consistently below 25% (Table 2). The average infection rates for these varieties were as follows: CH60 at 3.2%, CP37 at 3.8%, CP158 at 2.9%, CJ3056 at 2.6%, and QX3009 at 1.6%. These resources are ideal candidates for further breeding and large-scale promotion. 5.2 Case study: breeding for virus resistance Sweet potato virus disease (SPVD) is one of the most significant biotic constraints affecting sweet potato production, causing yield reductions ranging from 50% to 98%. Breeding for resistance to SPVD has been a primary focus to mitigate these losses. Traditional breeding methods face challenges such as reduced flowering, fertility issues, and self- or cross-incompatibility. Despite these challenges, the development of resistant varieties remains the most effective and economical method for small-scale farmers. Non-conventional breeding techniques, including marker-assisted selection and genetic engineering, offer promising complementary roles in enhancing resistance to SPVD (Ngailo et al., 2013).
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