Molecular Plant Breeding 2024, Vol.15, No.3, 132-143 http://genbreedpublisher.com/index.php/mpb 135 3.2 Significant achievements in tree breeding using MAS 3.2.1 Disease resistance One of the significant achievements in tree breeding using MAS is the development of disease-resistant tree varieties. By identifying and selecting genetic markers associated with disease resistance, breeders have been able to produce trees that are less susceptible to pathogens, thus reducing the need for chemical treatments and enhancing sustainability. For example, MAS has been effectively used to develop disease-resistant varieties of Cryptomeria japonica by targeting the MALE STERILITY 1(MS1) gene (Moriguchi et al., 2020). Moriguchi et al. (2020) applied marker-assisted selection (MAS) technology in Japanese cedar (Cryptomeria japonica) to effectively identify trees carrying the male sterility gene (MS1). In two families constructed through artificial crossing, markers closely linked to the MS1 gene were successfully identified. Additionally, the study used MAS technology to screen 650 trees, significantly reducing the time and labor required to select suitable breeding materials. This provides an effective tool for future tree breeding and has potential value in addressing issues related to allergic pollinosis. 3.2.2 Growth and yield improvement MAS has also contributed to significant improvements in the growth and yield of tree species. By selecting for genetic markers associated with rapid growth and high yield, breeders have been able to develop tree varieties that meet the increasing demands for wood and other forest products. This has been particularly effective in species such as Eucalyptus, where MAS has facilitated the rapid identification of high-yielding genotypes (Degen and Müller, 2023). 3.2.3 Wood quality enhancement Enhancing wood quality is another area where MAS has made substantial contributions. By identifying markers linked to desirable wood properties, such as density and fiber length, breeders have been able to select for trees that produce higher quality wood, which is essential for various industrial applications. This has led to the development of tree varieties with superior wood characteristics, benefiting both the timber and pulp industries (Grattapaglia, 2022). 3.3 Case studies The integration of advanced genomic technologies and MAS has led to significant breakthroughs in tree breeding, enhancing disease resistance, growth, yield, and wood quality. These advancements underscore the potential of MAS to drive the future of tree breeding and forestry. 3.3.1 Case 1: disease resistance in apple trees Apple breeding programs have successfully used MAS to develop disease-resistant varieties. Patocchi et al. (2020), through the international collaboration project VINQUEST, successfully utilized marker-assisted selection (MAS) to develop new apple varieties with durable resistance to apple scab by incorporating multiple resistance genes (Rvi5, Rvi11, Rvi12, Rvi14, and Rvi15). The research strategy involved combining multiple resistance genes within a single variety to create a "gene pyramid," enhancing the stability and durability of resistance. Analysis of data from 14 countries revealed that while some genes like Rvi1, Rvi3, and Rvi8 were often overcome, genes such as Rvi5, Rvi11, Rvi12, Rvi14, and Rvi15 exhibited excellent disease resistance stability. The outcomes of this study will enhance the efficiency of apple breeding, reduce pesticide use, and promote sustainable agricultural development (Figure 2). Figure 2 provides a visual assessment of the resistance performance of different apple resistance genes across multiple test locations and years, aiding in the evaluation and selection of genes with high disease resistance. Each box plot represents the distribution of resistance scores for a specific resistance gene across all test locations and years. The thick black line indicates the median, the box encompasses 50% of the data, and the whiskers cover most of the extreme values. From the figure, it can be observed that some genes, such as Rvi11 and Rvi15, have generally low resistance scores, indicating strong disease resistance. In contrast, genes like Rvi1 and Rvi3 have higher resistance scores, suggesting weaker resistance that is more easily overcome by pathogens.
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