Yellow Mosaic Virus (YMV) continues to pose a serious threat to legume production, particularly in tropical and subtropical regions where crops like mungbean, urdbean and soybean are extensively cultivated. The disease manifests through symptoms such as leaf yellowing, mosaic patterns and overall stunted plant growth, often leading to substantial yield reductions. As YMV is predominantly transmitted by the whitefly (
Bemisia tabaci), its control is further complicated by the insect’s high mobility and adaptability. Conventional management practices including vector control and agronomic adjustments have proven inadequate, primarily due to environmental limitations and the virus’s genetic variability
(Karthikeyan et al., 2014; Singh et al., 2018).
Given these challenges, resistance breeding has gained prominence as a sustainable and environmentally sound approach to mitigating YMV impact. In recent years, researchers have made considerable strides in discovering resistant genetic resources, identifying resistance loci and implementing molecular tools such as marker-assisted selection to expedite breeding efforts
(Chakraborty et al., 2020; Kumar et al., 2021). Furthermore, the integration of high-throughput genomics, transcriptomic profiling and genome-editing technologies has significantly advanced the development of YMV-resistant cultivars. This review aims to synthesize recent progress in resistance breeding against YMV, emphasizing gene discovery, breeding strategies and biotechnological innovations that contribute to durable and broad-spectrum resistance.
Yellow mosaic virus in blackgram
According to
Kumar et al., (2021), Yellow Mosaic Virus (YMV) represents a serious viral threat to blackgram (
Vigna mungo), particularly in tropical and subtropical climates. The disease is attributed to begomoviruses, mainly Mungbean Yellow Mosaic Virus (MYMV) and Mungbean Yellow Mosaic India Virus (MYMIV), both characterized as single-stranded DNA viruses. These pathogens are predominantly spread by the whitefly (
Bemisia tabaci). Due to its devastating impact, YMV is a primary focus in breeding initiatives aiming to develop resistant or tolerant blackgram varieties. Although a single whitefly can contract the virus and spread it to plants, female B. tabaci are typically more active and successful in spreading the virus than their male counterparts. Ten whiteflies per plant guaranteed 100% transmission, while a single viruliferous whitefly might spread the virus
(Swathi et al., 2023). Growing data, however, has started to refute this presumption. A number of begomoviruses, including sweet potato leaf curl virus (SPLCV) in sweet potatoes, MYMV in blackgram, bitter gourd yellow mosaic virus (BgYMV) in bitter gourds, dolichos yellow mosaic virus (DoYMV) in lablab and ToLCNDV in bitter gourds and chayotes, have been shown to transmit seeds in recent investigations
(Renukadevi et al., 2022). Characterization of YMD resistance using various advanced molecular and biochemical approaches during plant–virus interactions has unfolded a comprehensive network of pathogen survival, disease severity and the response of plants to pathogen attack, including mechanisms of YMD resistance in mungbean were reviewed througly
(Mishra et al., 2020).
Symptoms and economic impact
Symptoms
According to
Biswas et al., (2019), early signs often include the emergence of small yellow specks, which gradually enlarge into broader mosaic or chlorotic patches (as yellow and green mottling on leaves). As the disease progresses, infected foliage becomes malformed and plant growth is significantly inhibited. The disease adversely affects flowering and pod formation, ultimately resulting in reduced yield. In cases of severe infestation, fields may exhibit widespread yellowing, diminished vigor and even plant mortality
(Kumar et al., 2020). Trends have been reported in mungbean and with several
B. tabaci biotypes, highlighting the significance of extended acquisition for effective inoculation and symptom development
(Ambarish et al., 2023). Although vector-mediated transmission has historically been the main focus of begomovirus epidemiology, more recent research has shown how sophisticated and highly adaptive
B. tabaci is in acquiring and spreading MYMV, even during brief exposure periods (
Sandra and Mandal., 2024). MYMV has been found in a number of seed tissues, including the embryonic axis and has been shown to spread from seed to seedling in vulnerable cultivars like CO 5
(Niresh et al., 2024). The seed-borne nature of MYMIV in mungbean cultivars Pusa 1371 and Pusa 9531 using DAC-ELISA, PCR and progeny tests across three seasons
(Swamy et al., 2025). In order to calculate whitefly numbers, tomato plants were chosen at random in a zigzag pattern throughout each field. Adult whiteflies were counted on the top, middle and bottom leaves of ten randomly selected plants per field in the morning, when insect activity was at its lowest
(Sujatha et al., 2025). Okra enation leaf curl virus (OELCuV) seed transmissibility in bhendi hybrids, verifying its existence in asymptomatic seedlings using PCR and ELISAs
(Alagu et al., 2025).
Economic impact
YMD has a profound economic impact on blackgram production, especially across tropical and subtropical regions such as India. The disease is vectored by the whitefly
Bemisia tabaci, which contributes to its rapid dissemination
(Singh et al., 2018). Yield reductions vary depending on the severity and timing of infection, ranging from 30% to total crop loss in epidemic conditions. As reported by
Reddy and Ramesh (2021), the disease incurs economic losses not only through reduced yields but also through increased costs associated with insecticide application, decreased seed viability and lower market value of the harvest. This makes YMD a significant constraint on farmer income and regional food security.
Sources of resistance
Both cultivated varieties and wild relatives of
Vigna mungo have been found to possess resistance to Yellow Mosaic Virus (YMV).
Poehlman (1991) highlighted that a range of resistance exists within cultivated blackgram lines, as identified through early screening trials. Notably, genotypes such as VBN 6, VBN 8 and PU 31 have consistently displayed resistance when exposed to natural disease pressure (
IIPR, 2019).
Wild relatives, especially
Vigna mungo var. silvestris, have emerged as vital sources of resistance genes due to their genetic diversity and stable resistance traits
(Saxena et al., 2005). These have been incorporated into breeding programs using methods such as backcrossing and marker-assisted selection to improve cultivated varieties. Extensive screening of germplasm collections at the National Bureau of Plant Genetic Resources (NBPGR) led
Sharma et al., (2011) to identify promising resistant lines like IC 343936, IC 282094 and IC 281997. These accessions were found to maintain resistance across varied locations and seasons.
Singh et al., (2014) reported that genotype T9 exhibited moderate resistance, while Pant U-19 demonstrated effective field-level tolerance to YMV, particularly in northern India. Recent progress in molecular techniques has also allowed the identification of quantitative trait loci (QTLs) associated with YMV resistance. Genotypes such as Mash 114 and Mash 338 have been identified with linked markers and are now widely used as resistance donors in breeding programs
(Kumar et al., 2020). MYMIV-M120 (FM202447) and MYMV-Vigna (AJ132574) were found to be the major and minor parents of a large recombination event that was discovered in silico in the entire DNA-B in a work that contributed to the Frontiers in Plant Science inverted repeat (IR) area. This demonstrates unequivocally that the DNA-B of the MYMV-ThC15-India study is a recombinant, with a CR from MYMIV and most of the sequence taken from MYMV. For begomoviruses, this component exchange process also referred to as pseudo-recombination has been documented for the Indian recombinant DNA-B
(Chowdary et al., 2022).
Screening and evaluation techniques
Reliable screening methods form the foundation of successful resistance breeding against Yellow Mosaic Virus (YMV). Typically, two key approaches are employed: natural field screening and artificial inoculation, both of which are increasingly supported by molecular tools.
Natural field screening
In natural field screening, genotypes are evaluated in hotspot areas where the disease is prevalent, ensuring adequate vector (whitefly) populations and uniform disease pressure.
Varma and Malathi (2003) emphasized the effectiveness of this method when trials are conducted under consistent environmental conditions that favor YMV outbreaks. The screening of 100 blackgram genotypes for Mungbean Yellow Mosaic Virus (MYMV) disease under natural epiphytotic condition during summer-2018 season revealed that 33 genotypes were resistant to MYMV disease
(Sidramappa et al., 2025). Similarly,
Kumari et al. (2020) also reported MYMV resistant genotypes from their investigation. The investigation on MYMV through seed transmissible in blackgram, with latent and asymptomatic infections serving as hidden inoculum sources that complicate virus-free seed production and enhance the risk of long-distance spread through seed trade
(Sariga et al., 2025).
Artificial inoculation
For more precise evaluation, artificial inoculation techniques have been developed. These involve using whiteflies that carry the virus to infect test plants in controlled settings such as insect-proof cages or greenhouses. This method allows researchers to uniformly expose seedlings at a young stage, enabling the assessment of resistance based on symptom development. Standardized disease rating scales commonly ranging from 0 to 9 are used to quantify severity
(Kumar et al., 2009; Singh et al., 2011). The agro inoculated samples, by co-delivering MYMV DNA-A and DNA-B, showed more efficacy in the identification of resistant sources compared with field screening, as reported by various researchers the “agroinoculation” technique, a different approach that uses the Ti plasmid of the Agrobacterium for viral infection, has become superior to other phenotyping techniques in terms of infection pattern accuracy and the speed of identification of both resistant and susceptible cultivars
(Madhumitha et al., 2022). Dimeric MYMV infectious clones were constructed and the infectivity was confirmed through agro-inoculation and In future prospects, unless relying on screening using whiteflies, breeders and plant pathologists can readily use this agro-inoculation procedure to identify resistant and susceptible cultivars to YMD (
Madhumitha et al., 2024).
Molecular screening
To complement these phenotypic methods, molecular screening has become a valuable tool. The use of DNA markers like SSRs, RAPDs and SCARs linked to resistance loci enables early and accurate identification of resistant genotypes, even in the absence of disease symptoms. This technique has been successfully applied in lines such as Mash 114 and VBN 5 (
Souframanien and Gopalakrishna, 2004;
Gupta et al., 2013).
High-throughput phenotyping
Emerging high-throughput phenotyping technologies, including digital image analysis and spectral sensors, offer objective disease assessment. Although still in early stages for YMV research, these tools hold promise for improving screening precision
(Ramesh et al., 2020). Furthermore, the use of multi-location trials ensures the selection of genotypes with stable resistance across diverse environmental conditions, thereby enhancing the durability of resistance.
Conventional breeding approaches
Traditional breeding methods have been instrumental in the development of blackgram varieties resistant to Yellow Mosaic Virus (YMV). Initial breeding efforts primarily employed techniques such as pedigree selection, backcrossing and pure line selection to transfer resistance traits from donor lines into high-yielding backgrounds. These strategies relied heavily on observable traits and required continuous selection over multiple generations under natural disease pressure
(Sundaram et al., 2002). Among these methods, backcross breeding proved particularly successful, enabling the integration of YMV resistance along with desirable agronomic characteristics like early maturity and improved yield. Wild relatives like
Vigna mungo var.
silvestris and resistant cultivars such as Mash 114 and PU 31 have frequently been used as donors. One of the notable outcomes of this approach is the development of the variety VBN 3, which combines YMV resistance with good productivity
(Chandrababu et al., 2011). Another significant release, LBG 752, showcases the effectiveness of multi-parent crosses and rigorous selection carried out in YMV hotspot locations. This variety exhibits moderate resistance and performs well across varied environments
(Reddy et al., 2010). Some breeding programs have also applied recurrent selection and population improvement methods to gradually accumulate minor resistance genes. Although these methods require more time and effort, they have contributed to the steady enhancement of resistance within breeding populations
(Subramaniyan et al., 2006). Major research institutes such as Tamil Nadu Agricultural University (TNAU), the Indian Institute of Pulses Research (IIPR) and other State Agricultural Universities have played a key role in screening diverse germplasm collections and segregating populations. Their efforts have led to the release of improved YMV-resistant varieties like VBN 5, VBN 6 and Pant U-31, which offer better resistance against current virus strains (
IIPR, 2019). Despite these advancements, conventional breeding faces challenges, particularly in detecting latent infections and relying on natural whitefly infestations, which may vary seasonally. These limitations have led to the integration of molecular breeding tools to enhance the precision and efficiency of resistance breeding.
Marker-assisted selection (MAS)
Marker-Assisted Selection (MAS) has become a critical component in modern plant breeding, especially for legume crops like black gram, where improving resistance to diseases and tolerance to environmental stresses is essential. Conventional breeding methods for traits such as resistance to Yellow Mosaic Virus (YMV) often face challenges due to their reliance on environmental conditions and the complex nature of trait inheritance. In contrast, MAS offers a more efficient alternative by enabling selection of plants based on molecular markers closely linked to desirable traits, even at early growth stages. In the case of black gram, various molecular markers have been utilized to identify regions of the genome associated with disease resistance. One of the pioneering efforts was by
Souframanien and Gopalakrishna (2004), who applied RAPD (Random Amplified Polymorphic DNA) and SSR (Simple Sequence Repeat) markers to analyze genetic diversity and detect associations with YMV resistance. Their research laid the groundwork for implementing marker-assisted approaches in black gram breeding, highlighting the potential of SSR markers due to their high level of polymorphism and consistent reproducibility. Following these foundational studies, more recent investigations have aimed to identify specific Quantitative Trait Loci (QTLs) related to YMV resistance. For instance,
Muthurajan et al. (2017) mapped QTLs linked to resistance in recombinant inbred line populations using SSR markers. These QTLs demonstrated stability across diverse environments, indicating their value for resistance breeding programs. The availability of such QTLs has enabled breeders to combine multiple resistance genes into superior cultivars, a strategy known as gene pyramiding which increases the durability of resistance and minimizes the risk of resistance breakdown from evolving pathogens. The progress in high-throughput genotyping techniques has further strengthened MAS applications in black gram.
Kaur et al., (2019) underscored the role of advanced molecular tools such as SNP genotyping and genome-wide association studies (GWAS), which allow for the precise detection of marker-trait associations across the genome. These tools have enhanced the efficiency of selecting for complex traits and have become integral to modern breeding workflows. Moreover, access to draft genome assemblies and transcriptomic resources has led to the development of functional markers, which can directly target gene regions responsible for resistance mechanisms
(Kaur et al., 2019). This advancement supports the fine-mapping of resistance genes and the creation of diagnostic markers suitable for rapid, large-scale screening in breeding populations. In summary, MAS has greatly advanced black gram improvement by enabling the accurate and efficient transfer and stacking of resistance genes. When combined with traditional breeding and cutting-edge genomic tools, MAS is expected to significantly expedite the creation of high-yielding, disease-resistant black gram varieties adapted to different growing environments.
Biotechnological approaches
Black gram an essential pulse crop grown widely across Asia, is often impacted by both biotic factors like yellow mosaic virus (YMV) and bruchid pests, as well as abiotic stresses including drought and salinity. Conventional breeding approaches, though effective to a degree, are often hindered by the polygenic nature of stress-related traits and the influence of environmental conditions. The advent of biotechnology has introduced more precise, efficient and time-saving tools that have greatly enhanced the pace and accuracy of trait improvement in black gram.
Genetic transformation
Despite its relatively poor response to tissue culture and transformation, black gram has been the subject of several efforts to introduce useful genes via
Agrobacterium-mediated transformation. Notably,
Rathore et al., (1998) demonstrated the successful insertion of the
cry1Ac gene, a Bt toxin, in related legumes to improve insect resistance. Inspired by this success, similar strategies are being attempted in black gram to introduce genes associated with pest resistance, abiotic stress tolerance and nutritional enhancement. However, the efficiency of transformation is still a major challenge due to regeneration limitations
(Kalia et al., 2018).
In vitro regeneration
Developing a dependable regeneration system is critical for successful genetic transformation and biotechnological applications. Techniques such as organogenesis and somatic embryogenesis have been explored, though results are often genotype-specific.
Anbazhagan et al., (2010) reported successful regeneration from cotyledonary node explants in black gram. Continued optimization of regeneration protocols remains a key step toward enabling genome editing and genetic engineering in this crop.
Functional genomics and transcriptomics
Transcriptomics has enabled the identification of gene expression profiles under different stress conditions in black gram. These studies have revealed stress-responsive genes, regulatory elements and metabolic pathways involved in plant defence. For instance,
Kaur et al., (2019) conducted transcriptome sequencing in YMV-infected plants and identified a set of differentially expressed genes, which were later used to develop functional markers like genic SSRs. These findings have significantly contributed to trait-targeted breeding.
Genome editing (CRISPR/Cas9)
Although genome editing using CRISPR/Cas9 is still in the exploratory phase for black gram, it offers considerable promise for the precise improvement of complex traits. Researchers are focusing on developing transformation-compatible genotypes and targeting key genes involved in disease susceptibility, drought tolerance and nutritional quality. For example, future applications may include knocking out genes related to anti-nutritional compounds such as phytic acid. However, the lack of a robust transformation system currently restricts the widespread adoption of this technology.
Genomic resources and bioinformatics tools
The release of the black gram draft genome by
Paritosh et al., (2021) has significantly boosted genomic research in this crop. These resources support the identification of trait-associated genes, enable high-resolution QTL mapping and facilitate genome-wide association studies (GWAS). Online platforms such as PulseDB, NCBI and LegumeInfo have provided access to large-scale genomic datasets, making comparative genomics and bioinformatics-driven breeding more accessible and efficient.
Challenges in breeding for durable resistance
Breeding black gram varieties that exhibit long-lasting resistance to pests and diseases continues to be a significant challenge, especially in areas where the crop is critical for food security. The process of developing durable resistance is complicated by several factors, including genetic diversity, environmental effects and technical limitations. Key threats such as Yellow Mosaic Virus (YMV) and bruchid beetles, alongside stresses induced by climate variability, make the breeding process even more complex.
High variability of pathogens and pests
A major difficulty in securing durable resistance lies in the rapid genetic changes and adaptability of the pests and pathogens themselves. For instance, YMV, a begomovirus transmitted by whiteflies (
Bemisia tabaci), displays considerable mutation and strain diversity across regions, which undermines the stability of resistance in black gram cultivars
(Karthikeyan et al., 2014). Likewise, bruchid beetles (
Callosobruchus species), known for damaging stored seeds, evolve quickly and can overcome resistance within a few generations
(Somta et al., 2019). This dynamic interaction between host and pest/pathogen frequently leads to resistance breakdown in newly developed varieties.
Complex inheritance of resistance traits
Resistance traits in black gram are often controlled by multiple genes, exhibiting quantitative inheritance patterns. Such traits tend to have low heritability and show significant interaction with environmental factors, complicating their selection and stabilization through classical breeding approaches
(Muthurajan et al., 2017; Kumar et al., 2020). Furthermore, stacking several quantitative trait loci (QTLs) for durable resistance requires sophisticated phenotyping and molecular tools that are not yet fully optimized for black gram.
Limited genetic diversity
Compared to other important legumes like soybean and chickpea, black gram has a relatively narrow genetic base in breeding programs. This restricts the pool of novel resistance genes available, especially against newly emerging or evolving pest and pathogen strains (
Souframanien and Gopalakrishna, 2004). Although wild relatives possess valuable resistance traits, their use is limited by crossbreeding difficulties and the possibility of introducing undesirable traits (linkage drag)
(Nair et al., 2019).
Insufficient molecular and genomic resources
Despite progress in molecular breeding, the development of dense genetic maps, comprehensive genome sequences and functional markers for black gram remains inadequate. These gaps limit the effectiveness of marker-assisted selection (MAS) and related technologies
(Paritosh et al., 2021). Additionally, transformation protocols and genome editing tools like CRISPR/Cas9 have not yet been fully established, which hinders the functional analysis of candidate resistance genes
(Kalia et al., 2018).
Influence of environmental conditions
Environmental variables, particularly temperature and humidity, greatly affect the expression of resistance traits. For example, elevated temperatures can reduce the effectiveness of YMV resistance and enhance whitefly populations, increasing disease incidence (
Varma and Malathi, 2003). This environmental sensitivity complicates accurate phenotyping and selection, often resulting in inconsistent resistance evaluations.
Scarcity of durable resistance genes
Most resistance genes identified for YMV in black gram confer race-specific or vertical resistance, which is typically short-lived when exposed to a diverse pathogen population
(Maiti et al., 2011). Therefore, there is a critical need to discover and deploy broad-spectrum, or horizontal, resistance genes that confer more stable and durable protection. However, identifying such genes remains challenging.
