Plant Gene and Traits 2024, Vol.15, No.4, 195-206 http://genbreedpublisher.com/index.php/pgt 196 2 Overview of Pests and Diseases Affecting Legumes 2.1 Common pests affecting legume crops Legume crops are susceptible to a variety of pests that can significantly impact their yield and quality. Among the most common pests are aphids and pod borers. Aphids are sap-sucking insects that can cause direct damage by feeding on plant sap and indirect damage by transmitting viral diseases. Pod borers, such as the legume pod borer (Maruca vitrata), are notorious for their destructive feeding habits on flowers, pods, and seeds, leading to substantial yield losses (Rubiales et al., 2015; Jha et al., 2023). 2.2 Major diseases impacting legumes Legume crops are affected by a wide range of diseases caused by fungal, bacterial, and viral pathogens. Fungal diseases such as rusts, powdery and downy mildews, ascochyta blights, botrytis gray molds, anthracnoses, damping-off, root rots, collar rots, vascular wilts, and white molds are particularly devastating (Rubiales et al., 2015; Pandey et al., 2023). Bacterial diseases, including common bacterial blight, halo blight, and bacterial brown spot, also pose significant threats to legume production. Viral diseases, such as Bean common mosaic virus (BCMV), Bean golden mosaic virus (BGMV), and Bean golden yellow mosaic virus (BGYMV), further complicate the management of legume crops (Jha et al., 2023). 2.3 Economic and yield losses due to pest and disease outbreaks in legume crops Pest and disease outbreaks in legume crops can lead to severe economic and yield losses. For instance, diseases like anthracnose and ascochyta blight can cause significant yield reductions, sometimes up to 100% in severe cases (Jha et al., 2022; Pandey et al., 2023). The economic impact is profound, as legumes are a crucial source of protein and income for many farmers, especially in developing countries. The cost of managing these pests and diseases, including the use of fungicides, insecticides, and resistant varieties, adds to the financial burden on farmers (Rubiales et al., 2015; Pandey et al., 2023). Additionally, the continuous evolution of pathogens and pests under high selection pressure necessitates ongoing research and development of new resistant cultivars to sustain legume production (Martins et al., 2020; Saxena et al., 2023). 3 Conventional Breeding for Pest and Disease Resistance 3.1 Traditional breeding strategies used to develop resistant legume varieties Traditional breeding strategies for developing pest and disease-resistant legume varieties have primarily relied on the selection and cross-breeding of plants exhibiting desirable traits (Zhou and Guo, 2024). Phenotypic selection involves selecting plants that show natural resistance to pests and diseases and using them as parents in breeding programs. For example, in common beans, breeders have used phenotypic selection to develop cultivars with enhanced levels of disease and pest resistance (Basavaraja et al., 2020). Cross-breeding between resistant and susceptible varieties to combine desirable traits. In lentils, wide hybridization and ovule rescue techniques have been employed to introgress resistance traits from wild relatives into cultivated varieties. Induced mutagenesis creates genetic variability through mutagenesis to develop disease-resistant lines. This approach has been used in lentils to develop several disease-resistant mutant lines (Roy et al., 2023). Utilize related species to introduce resistance genes. For instance, interspecific hybridizations with Phaseolus coccineus and Phaseolus acutifolius have been used to introduce disease resistance in common beans. 3.2 Limitations of conventional breeding in achieving durable resistance Despite the successes, conventional breeding faces several limitations in achieving durable resistance. The process of developing resistant varieties through traditional breeding methods can take 7~10 years, requiring significant economic resources (Basavaraja et al., 2020). Traits such as resistance to multiple pathogens and environmental stressors are often complex and controlled by multiple genes, making them difficult to select and breed for using conventional methods (Basavaraja et al., 2020). The effectiveness of resistance traits can vary significantly across different environments, complicating the selection process. The genetic base of cultivated varieties is often narrow, limiting the availability of resistance genes (Rubiales et al., 2015). Pathogens can evolve and overcome resistance, necessitating continuous breeding efforts to keep up with new strains (Wille et al., 2018).
RkJQdWJsaXNoZXIy MjQ4ODYzMg==