Exploring Marker-Trait Associations for Resistance to Cercospora Leaf Spot in Mung Bean
Description
Introduction
Mung bean (Vigna radiata (L.) Wilczek) is a crucial legume crop, widely cultivated for its high protein content and adaptability in various climates (Pattnaik et al., 2024). However, its productivity is significantly hampered by biotic stress, Cercospora leaf spot (CLS), caused by the fungus Cercospora canescens, being one of the most damaging diseases affecting mung bean crops worldwide (Sahoo, 2022a). This disease leads to reduced photosynthesis, premature leaf drop, and ultimately, lower yields, and developing mung bean varieties resistant to CLS is an urgent priority for breeders to safeguard production (Sahoo et al., 2022b).. This study focuses on identifying genetic markers associated with CLS resistance and mapping the quantitative trait loci (QTLs) responsible for this resistance (Sahoo, 2022a).
Key Challenges
The primary challenge in combating CLS in mung bean is the genetic complexity underlying resistance to the disease. CLS resistance is controlled by multiple genes and environmental factors, making it difficult to improve through conventional breeding alone. Additionally, mung bean is a crop with limited genetic resources, making it challenging to identify resistance traits in existing cultivars. Another difficulty lies in accurately detecting and mapping QTLs that influence resistance, as the genetic architecture of CLS resistance is not well understood. In this study, a major challenge was developing a population with sufficient genetic diversity to conduct effective association mapping. The panel population had to represent a wide range of mung bean genotypes, capturing the variability for CLS resistance. Furthermore, the complexity of marker-trait associations required advanced statistical models and computational tools to ensure the accurate identification of the relevant QTLs (Sahoo et al., 2022c).
Methodology
To tackle these challenges, a panel population of 90 mung bean genotypes was created for association mapping. The genotypes were selected to represent diverse genetic backgrounds and varying degrees of resistance to CLS. The research used 66 simple sequence repeat (SSR) markers to assess genetic diversity and population structure. The genotypes were classified using three different software tools—GenAlEx 6.51b2, TASSEL 5.0, and STRUCTURE V.2.3.4—based on their genetic relationships and cluster patterns. The stress resistance of each genotype was evaluated under field as well as controlled environmental conditions, and a marker-trait association study was conducted to identify genetic loci associated with CLS resistance. The analysis was performed using both the generalized linear model (GLM) and the mixed linear model (MLM) (Sahoo et al., 2023a).
Findings
The results revealed significant variation in CLS resistance among the mung bean genotypes, highlighting the potential for genetic improvement. Two distinct genetic clusters were identified within the population, indicating that the genotypes could be grouped into two broad genetic backgrounds. This clustering was essential for understanding the genetic structure of the population and interpreting the results of the association mapping study. Marker-trait association analysis led to the identification of two key markers, CEDG006 and CEDG071, which were strongly associated with CLS resistance. These markers could potentially serve as reliable tools for selecting resistant genotypes in future breeding programs. Additionally, the study identified two novel QTLs controlling CLS resistance, designated as qCls_2 and qCls_8. These QTLs represent important genetic regions that regulate resistance to the disease and could be targeted for introgression into elite mung bean varieties. Beyond CLS resistance, the study also discovered novel QTLs for other agronomic traits, including plant height (qPht_8), number of clusters (qNcl_6 and qNcl_10), hundred seed weight (qHsw_3 and qHsw_11), and yield (qYld_2, qYld_7, and qYld_8) under CLS stress (Sahoo et al., 2023b).
Impact of the Work
The identification of novel QTLs and marker-trait associations for CLS resistance in mung beans has significant implications for crop improvement. The two QTLs (qCls_2 and qCls_8) associated with CLS resistance can be used in marker-assisted selection (MAS) to develop mung bean varieties with enhanced disease resistance. These resistant varieties will be crucial for improving mung bean yields in regions heavily affected by CLS, ultimately increasing food security and farmer livelihoods. The discovery of additional QTLs for agronomic traits like plant height, number of clusters, seed weight, and yield under stress also contributes to the overall improvement of mung bean productivity. By incorporating these QTLs into breeding programs, it is possible to develop high-yielding, disease-resistant varieties, which is a major step towards sustainable mung bean production in the face of biotic stresses like CLS. Moreover, the study’s findings open avenues for further research into the genetic basis of disease resistance and other key traits in mung bean. The QTLs identified in this study should be validated in diverse germplasms to assess their stability and broader applicability. This could lead to the development of a more resilient and high-performing mung bean cultivar.
Conclusion
This research represents a significant step forward in understanding the genetic basis of CLS resistance in mung bean. The identification of marker-trait associations and novel QTLs provides essential tools for breeders to enhance disease resistance and improve crop productivity. The use of advanced genomic tools in association mapping has the potential to accelerate the breeding of high-yielding, disease-resistant mung bean varieties. By incorporating the findings from this study into breeding programs, it is possible to mitigate the impact of CLS on mung bean production, ultimately benefiting both farmers and consumers.
References
Pattnaik, S., Sahoo, J. P., Mahapatra, M., Das, B. P., Parween, A., & Sunani, S. K. (2024). Morpho-biochemical and Molecular Characterization of New Mung Bean [Vigna radiata (L.) Wilczek] Landraces for Cercospora Leaf Spot (CLS) Disease Resistance. Physiological and Molecular Plant Pathology, 102448. https://doi.org/10.1016/j.pmpp.2024.102448
Sahoo, J. P. (2022a). Marker trait association studies for resistance to Cercospora Leaf Spot (CLS) in Mung bean [Vigna radiata (L.) Wilczek] (Doctoral dissertation, Department of Agricultural Biotechnology, OUAT, Bhubaneswar). https://krishikosh.egranth.ac.in/items/4b151c97-1f4d-4498-9036-73993623796f
Sahoo, J. P., Mahapatra, M., Mohapatra, M., and Samal, K. C. (2023a). Morpho-genetic assessment and dissecting the genetic architecture for Cercospora leaf spot (CLS) resistance in mung bean [Vigna radiata (L.) Wilczek]. Physiological and Molecular Plant Pathology, 128, 102178. https://doi.org/10.1016/j.pmpp.2023.102178
Sahoo, J. P., Samal, K. C., Lenka, D., and Behera, L. (2023b). Population genetic structure and marker-trait association studies for Cercospora leaf spot (CLS) resistance in mung bean (Vigna radiata (L.) Wilczek). Tropical Plant Pathology, 48(3), 303-318. https://doi.org/10.1007/s40858-023-00565-w
Sahoo, J. P., Samal, K. C., Lenka, D., Beura, S. K., Behera, L., Khamari, B., and Sawant, S. B. (2022b). Assessment of Genetic Diversity for Cercospora Leaf Spot (CLS) Resistance in Mung Bean [Vigna radiata (L.) Wilczek] using SSR Markers. Legume Research-An International Journal, 47 (2): 312-317. https://doi.org/10.18805/LR-4985
Sahoo, J. P., Samal, K. C., Tripathy, S. K., Lenka, D., Mishra, P., Behera, L., ... & Behera, B. (2022c). Understanding the genetics of Cercospora leaf spot (CLS) resistance in mung bean (Vigna radiata L. Wilczek). Tropical Plant Pathology, 47(6), 703-717. https://doi.org/10.1007/s40858-022-00525-w
Mung bean (Vigna radiata (L.) Wilczek) is a crucial legume crop, widely cultivated for its high protein content and adaptability in various climates (Pattnaik et al., 2024). However, its productivity is significantly hampered by biotic stress, Cercospora leaf spot (CLS), caused by the fungus Cercospora canescens, being one of the most damaging diseases affecting mung bean crops worldwide (Sahoo, 2022a). This disease leads to reduced photosynthesis, premature leaf drop, and ultimately, lower yields, and developing mung bean varieties resistant to CLS is an urgent priority for breeders to safeguard production (Sahoo et al., 2022b).. This study focuses on identifying genetic markers associated with CLS resistance and mapping the quantitative trait loci (QTLs) responsible for this resistance (Sahoo, 2022a).
Key Challenges
The primary challenge in combating CLS in mung bean is the genetic complexity underlying resistance to the disease. CLS resistance is controlled by multiple genes and environmental factors, making it difficult to improve through conventional breeding alone. Additionally, mung bean is a crop with limited genetic resources, making it challenging to identify resistance traits in existing cultivars. Another difficulty lies in accurately detecting and mapping QTLs that influence resistance, as the genetic architecture of CLS resistance is not well understood. In this study, a major challenge was developing a population with sufficient genetic diversity to conduct effective association mapping. The panel population had to represent a wide range of mung bean genotypes, capturing the variability for CLS resistance. Furthermore, the complexity of marker-trait associations required advanced statistical models and computational tools to ensure the accurate identification of the relevant QTLs (Sahoo et al., 2022c).
Methodology
To tackle these challenges, a panel population of 90 mung bean genotypes was created for association mapping. The genotypes were selected to represent diverse genetic backgrounds and varying degrees of resistance to CLS. The research used 66 simple sequence repeat (SSR) markers to assess genetic diversity and population structure. The genotypes were classified using three different software tools—GenAlEx 6.51b2, TASSEL 5.0, and STRUCTURE V.2.3.4—based on their genetic relationships and cluster patterns. The stress resistance of each genotype was evaluated under field as well as controlled environmental conditions, and a marker-trait association study was conducted to identify genetic loci associated with CLS resistance. The analysis was performed using both the generalized linear model (GLM) and the mixed linear model (MLM) (Sahoo et al., 2023a).
Findings
The results revealed significant variation in CLS resistance among the mung bean genotypes, highlighting the potential for genetic improvement. Two distinct genetic clusters were identified within the population, indicating that the genotypes could be grouped into two broad genetic backgrounds. This clustering was essential for understanding the genetic structure of the population and interpreting the results of the association mapping study. Marker-trait association analysis led to the identification of two key markers, CEDG006 and CEDG071, which were strongly associated with CLS resistance. These markers could potentially serve as reliable tools for selecting resistant genotypes in future breeding programs. Additionally, the study identified two novel QTLs controlling CLS resistance, designated as qCls_2 and qCls_8. These QTLs represent important genetic regions that regulate resistance to the disease and could be targeted for introgression into elite mung bean varieties. Beyond CLS resistance, the study also discovered novel QTLs for other agronomic traits, including plant height (qPht_8), number of clusters (qNcl_6 and qNcl_10), hundred seed weight (qHsw_3 and qHsw_11), and yield (qYld_2, qYld_7, and qYld_8) under CLS stress (Sahoo et al., 2023b).
Impact of the Work
The identification of novel QTLs and marker-trait associations for CLS resistance in mung beans has significant implications for crop improvement. The two QTLs (qCls_2 and qCls_8) associated with CLS resistance can be used in marker-assisted selection (MAS) to develop mung bean varieties with enhanced disease resistance. These resistant varieties will be crucial for improving mung bean yields in regions heavily affected by CLS, ultimately increasing food security and farmer livelihoods. The discovery of additional QTLs for agronomic traits like plant height, number of clusters, seed weight, and yield under stress also contributes to the overall improvement of mung bean productivity. By incorporating these QTLs into breeding programs, it is possible to develop high-yielding, disease-resistant varieties, which is a major step towards sustainable mung bean production in the face of biotic stresses like CLS. Moreover, the study’s findings open avenues for further research into the genetic basis of disease resistance and other key traits in mung bean. The QTLs identified in this study should be validated in diverse germplasms to assess their stability and broader applicability. This could lead to the development of a more resilient and high-performing mung bean cultivar.
Conclusion
This research represents a significant step forward in understanding the genetic basis of CLS resistance in mung bean. The identification of marker-trait associations and novel QTLs provides essential tools for breeders to enhance disease resistance and improve crop productivity. The use of advanced genomic tools in association mapping has the potential to accelerate the breeding of high-yielding, disease-resistant mung bean varieties. By incorporating the findings from this study into breeding programs, it is possible to mitigate the impact of CLS on mung bean production, ultimately benefiting both farmers and consumers.
References
Pattnaik, S., Sahoo, J. P., Mahapatra, M., Das, B. P., Parween, A., & Sunani, S. K. (2024). Morpho-biochemical and Molecular Characterization of New Mung Bean [Vigna radiata (L.) Wilczek] Landraces for Cercospora Leaf Spot (CLS) Disease Resistance. Physiological and Molecular Plant Pathology, 102448. https://doi.org/10.1016/j.pmpp.2024.102448
Sahoo, J. P. (2022a). Marker trait association studies for resistance to Cercospora Leaf Spot (CLS) in Mung bean [Vigna radiata (L.) Wilczek] (Doctoral dissertation, Department of Agricultural Biotechnology, OUAT, Bhubaneswar). https://krishikosh.egranth.ac.in/items/4b151c97-1f4d-4498-9036-73993623796f
Sahoo, J. P., Mahapatra, M., Mohapatra, M., and Samal, K. C. (2023a). Morpho-genetic assessment and dissecting the genetic architecture for Cercospora leaf spot (CLS) resistance in mung bean [Vigna radiata (L.) Wilczek]. Physiological and Molecular Plant Pathology, 128, 102178. https://doi.org/10.1016/j.pmpp.2023.102178
Sahoo, J. P., Samal, K. C., Lenka, D., and Behera, L. (2023b). Population genetic structure and marker-trait association studies for Cercospora leaf spot (CLS) resistance in mung bean (Vigna radiata (L.) Wilczek). Tropical Plant Pathology, 48(3), 303-318. https://doi.org/10.1007/s40858-023-00565-w
Sahoo, J. P., Samal, K. C., Lenka, D., Beura, S. K., Behera, L., Khamari, B., and Sawant, S. B. (2022b). Assessment of Genetic Diversity for Cercospora Leaf Spot (CLS) Resistance in Mung Bean [Vigna radiata (L.) Wilczek] using SSR Markers. Legume Research-An International Journal, 47 (2): 312-317. https://doi.org/10.18805/LR-4985
Sahoo, J. P., Samal, K. C., Tripathy, S. K., Lenka, D., Mishra, P., Behera, L., ... & Behera, B. (2022c). Understanding the genetics of Cercospora leaf spot (CLS) resistance in mung bean (Vigna radiata L. Wilczek). Tropical Plant Pathology, 47(6), 703-717. https://doi.org/10.1007/s40858-022-00525-w
Dr. Jyoti Prakash Sahoo
Assistant Professor (Biotechnology)
Faculty of Agriculture and Allied Sciences
C.V. Raman Global University (CGU)
Bhubaneswar - 752054, Odisha, India
Prof. (Dr.) Kailash Chandra Samal
Dean, College of Horticulture
Odisha University of Agriculture and Technology
Chiplima - 768026, Odisha, India
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