Molecular Pathogens 2024, Vol.15, No.5, 246-254 http://microbescipublisher.com/index.php/mp 251 6.2 TAL effector-mediated disease in common bean: insights into pathogen-host interactions In common bean, TAL effectors fromXanthomonas spp. play a crucial role in disease development by activating host susceptibility genes. Comparative studies on TAL effectors from different Xanthomonas strains have highlighted the specificity and variability of these effectors in targeting host genes. For instance, research on Xanthomonas axonopodis pv. manihotis, which infects cassava, demonstrated that even minor variations in the repeat variable diresidues (RVDs) of TAL effectors can lead to differential activation of host genes. This finding underscores the precision with which TAL effectors can manipulate host gene expression, a mechanism likely mirrored in common bean infections (Cohn et al., 2016). The identification of conserved TAL effectors across different strains suggests a universal strategy employed by Xanthomonas to exploit common bean's genetic vulnerabilities. 6.3 Applications of TAL effector research in crop improvement The insights gained from studying TAL effectors in Xanthomonas-infected legumes have significant implications for crop improvement. By understanding the specific host genes targeted by TAL effectors, researchers can develop strategies to enhance resistance in legume crops. For example, targeted promoter editing using TAL effector nucleases (TALENs) has been successfully employed in rice to create resistance against Xanthomonas oryzae pv. oryzae by disrupting the binding sites of TAL effectors on susceptibility genes (Blanvillain-Baufumé et al., 2016). This approach can be adapted for legumes, where editing the promoters of key susceptibility genes could confer resistance to Xanthomonas infections. The identification of conserved TAL effectors across different strains provides a basis for developing broad-spectrum resistance strategies that can protect multiple legume species from diverse Xanthomonas pathogens (Wilkins et al., 2015; Doucouré et al, 2022). 7 Control Strategies for Xanthomonas Infections in Legumes 7.1 Use of biological control agents against Xanthomonas Biological control agents (BCAs) offer a sustainable and eco-friendly approach to managing Xanthomonas infections in legumes. These agents include beneficial microorganisms such as bacteria, fungi, and viruses that can inhibit the growth or activity of Xanthomonas pathogens. For instance, certain strains of Bacillus and Pseudomonas have been shown to produce antimicrobial compounds that suppress Xanthomonas growth (Hutin et al., 2015). The use of phages specific to Xanthomonas species has been explored as a biocontrol strategy. These phages can infect and lyse the bacterial cells, thereby reducing the pathogen population in the field. The application of BCAs not only helps in controlling the disease but also promotes plant health by enhancing nutrient uptake and inducing systemic resistance in plants. 7.2 Chemical control methods Chemical control methods involve the use of bactericides and antibiotics to manage Xanthomonas infections. Copper-based compounds are commonly used bactericides that can effectively reduce the bacterial load on plant surfaces. However, the overuse of these chemicals can lead to the development of copper-resistant strains of Xanthomonas, necessitating the need for alternative or complementary strategies. Antibiotics such as streptomycin and oxytetracycline have also been employed to control bacterial diseases, but their use is often restricted due to concerns about antibiotic resistance and environmental impact (Denancé et al., 2018). Integrated approaches that combine chemical treatments with other control methods are recommended to minimize the risk of resistance development and ensure sustainable disease management. 7.3 Integrated disease management (IDM) Integrated Disease Management (IDM) is a holistic approach that combines multiple strategies to control Xanthomonas infections in legumes. IDM involves the integration of cultural practices, biological control, chemical treatments, and the use of resistant cultivars to achieve effective and sustainable disease management. Cultural practices such as crop rotation, proper irrigation management, and sanitation can reduce the initial inoculum and prevent the spread of the pathogen. The use of resistant cultivars, which possess genetic resistance to Xanthomonas, is a key component of IDM. Research has shown that certain resistance loci in crops can be
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