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Relative amount of DNA-A and DNA-B genome components of EACMV-UG Ca055 in non symptomatic (a) and symptomatic (b) leaf tissues and ACMV DRC6 in non symptomatic (c) and symptomatic (d) leaf tissues of cassava plants cv. TMS 30572. Red dot indicates value for DNA-A concentration; blue dot is value for DNA-B concentration (Ca numbers indicate individual plant codes designated for these experiments). (For interpretation of the references to color in this figure legend, the reader is referred to the web version of the article.)
Source publication
The quantity of genomic DNA-A and DNA-B of African cassava mosaic virus (ACMV) and East African cassava mosaic virus Uganda (Uganda variant, EACMV-UG) was analysed using quantitative PCR to assess virus concentrations in plants from susceptible and tolerant cultivars. The concentrations of genome components in absolute and relative quantification e...
Contexts in source publication
Context 1
... the improved cassava cultivar TMS 30572, for EACMV-UG Ca055 infection, DNA-B concentrations were higher than amounts of DNA-A in leaves expressing mosaic symptoms. Substantial amounts of EACMV DNA-A and DNA-B components were also found in the non-symptomatic leaves of this cv. (Fig. 5a and b). For ACMV infections in cv. TMS 30572, the ratio between DNA-A and DNA-B components was nearly 1:1 with only slight variations in the pro- portions of DNA-A and DNA-B in non-symptomatic tissues ( Fig. 5c and ...
Context 2
... mosaic symptoms. Substantial amounts of EACMV DNA-A and DNA-B components were also found in the non-symptomatic leaves of this cv. (Fig. 5a and b). For ACMV infections in cv. TMS 30572, the ratio between DNA-A and DNA-B components was nearly 1:1 with only slight variations in the pro- portions of DNA-A and DNA-B in non-symptomatic tissues ( Fig. 5c and ...
Context 3
... the improved cassava cultivar TMS 30572, for EACMV-UG Ca055 infection, DNA-B concentrations were higher than amounts of DNA-A in leaves expressing mosaic symptoms. Substantial amounts of EACMV DNA-A and DNA-B components were also found in the non-symptomatic leaves of this cv. (Fig. 5a and b). For ACMV infections in cv. TMS 30572, the ratio between DNA-A and DNA-B components was nearly 1:1 with only slight variations in the pro- portions of DNA-A and DNA-B in non-symptomatic tissues ( Fig. 5c and ...
Context 4
... mosaic symptoms. Substantial amounts of EACMV DNA-A and DNA-B components were also found in the non-symptomatic leaves of this cv. (Fig. 5a and b). For ACMV infections in cv. TMS 30572, the ratio between DNA-A and DNA-B components was nearly 1:1 with only slight variations in the pro- portions of DNA-A and DNA-B in non-symptomatic tissues ( Fig. 5c and ...
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Chicken infectious anemia virus (CIAV) can be transmitted by contaminated live vaccines, and causes huge economic losses. This study evaluated the contamination status of CIAV in 24 batches of vaccines by recombinase-aided amplification assay (RAA), fluorescence quantitative PCR and dot blot assay, and then found a contaminated attenuated vaccine....
Citations
... Cassava susceptibility or resistance to CMD varies with CMB species with EACMV considered more virulent inducing more severe symptoms (Bull et al. 2007). Additionally, natural mixed infections of EACMV-UG and ACMV gave severe disease symptoms (Naseem and Winter 2016). Kuria et al. (2017) studied differential response of cassava genotypes to infection by CMBs. ...
... The FC was calculated by comparing CMB-infected and CMB-free plants that were used to normalize β-actin Ct values, where ΔΔCt = (CT CMBinfected plants -CT β-actin of CMB-infected plant ) -(CT CMBinfected plant -CT β-actin of CMB-free plant ). Cassava β-actin has been validated by Naseem and Winter (2016) for use as an internal reference gene to normalize CT for CMB quantification using qPCR. Germplasms with CT values of 36 and above were considered too low to be detected and thus classified as CMB-free. ...
... Indeed, more severe CMD symptoms have been recorded in cassava plants with dual or multiple CMB infections due to synergistic viral interactions compared to either virus alone (Patil and Fauquet 2009;Pita et al. 2001;Harrison et al. 1997;Fondong et al. 2000). Virus concentrations corresponded with severity of disease symptoms (Naseem and Winter 2016). Dual-infected plants often collapse due to combination of two differential gene silencing suppressors from both viruses (Fauquet and Nawaz-ul-Rehman 2008). ...
Cassava mosaic disease (CMD) is caused by cassava mosaic begomoviruses (CMBs) vectored by whiteflies (Bemisia tabaci) and disseminated through infected stem cuttings. The disease severely inhibits cassava production sustaining incessant food insecurity and associated poverty in sub-Saharan Africa. Through farmer field surveys and molecular diagnostic assays, this study analyzed CMBs in sampled cassava landraces (LARs) and improved genotypes (IMGs) grown in the field by farmers in Kenya. Variations were significant between germplasms based on CMD symptom severity and incidences, CMB identity, infection levels, viral loads, and presence of sequences enhancing Geminivirus symptoms (SEGS) with most IMGs generally showing suppressed response to CMBs compared to more severe CMD effects on most LARs. Single to mixed infections between germplasms were recorded for five CMB species, African cassava mosaic virus (ACMV), East African cassava mosaic virus (EACMV), East African cassava mosaic Kenya virus (EACMKV), East African cassava mosaic Zanzibar virus (EACMZV), and EACMV-Ugandan variant (EACMV-UG). Detection of EACMV from Tanzania and the coast-endemic EACMZV in other regions of Kenya implied potential exchange or movement of infected planting materials by farmers. Correlations of viral loads with CMD severity were positive and significant. Both IMGs and LARs showed other complex relationships between different CMB infection levels, virus concentration, and associated SEGS that resulted in varied CMD symptom severity. Some IMGs that had been bred for CMD resistance, but showed high CMD severity in this study, indicated hypothetical breakdown of CMD resistance over time. Some CMB-free and SEGS-free IMGs and LARs were however identified and could be bulked for CMD-free cuttings for planting or used as breeding parental lines for population development and enrichment.
... DNA-B segments also affect viral host range (Idris et al., 2011) and determine symptoms and symptom severity (Von Arnim and Stanley, 1992;Jyothsna et al., 2013), even for an otherwise monopartite begomovirus (Ouattara et al., 2022). The DNA-B segment also appears to dominate reproduction in infected plants; quantitative PCR studies have shown that plants infected with bipartite begomoviruses have higher DNA-B accumulation than DNA-A accumulation (Péréfarres et al., 2012;Naseem and Winter, 2016). ...
Approximately half of the characterized begomoviruses have bipartite genomes, but the second genomic segment, the DNA-B, is understudied relative to the DNA-A, which is homologous to the entire genome of monopartite begomoviruses. We examined the evolutionary history of the two proteins encoded by the DNA-B, the genes of which make up ∼60% of the DNA-B segment, from all bipartite begomovirus species. Our dataset of 131 movement protein (MP) and nuclear shuttle protein (NSP) sequences confirmed the deep split between Old World (OW) and New World (NW) species, and showed strong support for deep, congruent branches among the OW sequences of the MP and NSP. NW sequences were much less diverse and had poor phylogenetic resolution; over half of nodes in both the NSP and MP NW clades were supported by <50% bootstrap support. This poor resolution hampered our ability to detect incongruent phylogenies between the MP and NSP datasets, and we found no statistical evidence for recombination within our MP and NSP datasets. Finally, we quantified the sequence diversity between the NW and OW proteins, showing that the NW MP has particularly low diversity, suggesting it has been subject to different evolutionary pressures than the NW NSP.
... Several molecular and serology-based methods have been employed for the detection of CMBs such as PCR [20], multiplex PCR [21], real-time PCR [22], immunosorbent electromicroscopy [23], double antibody sandwich enzyme-linked immunosorbent assay (DAS-ELISA) [24] and triple antibody sandwich-ELISA (TAS-ELISA) [25]. For SLCMV, methods such as PCR [26][27][28], multiplex PCR [29,30], rolling circle amplification (RCA) [12] and plate-trapped antigen-ELISA (PTA-ELISA) [15] have been described. ...
Background
Cassava mosaic disease (CMD) is one of the most devastating viral diseases for cassava production in Africa and Asia. Accurate yet affordable diagnostics are one of the fundamental tools supporting successful CMD management, especially in developing countries. This study aimed to develop an antibody-based immunoassay for the detection of Sri Lankan cassava mosaic virus (SLCMV), the only cassava mosaic begomovirus currently causing CMD outbreaks in Southeast Asia (SEA).
Methods
Monoclonal antibodies (MAbs) against the recombinant coat protein of SLCMV were generated using hybridoma technology. MAbs were characterized and used to develop a triple antibody sandwich enzyme-linked immunosorbent assay (TAS-ELISA) for SLCMV detection in cassava leaves and stems. Assay specificity, sensitivity and efficiency for SLCMV detection was investigated and compared to those of a commercial ELISA test kit and PCR, the gold standard.
Results
A TAS-ELISA for SLCMV detection was successfully developed using the newly established MAb 29B3 and an in-house polyclonal antibody (PAb) against begomoviruses, PAb PK. The assay was able to detect SLCMV in leaves, green bark from cassava stem tips, and young leaf sprouts from stem cuttings of SLCMV-infected cassava plants without cross-reactivity to those derived from healthy cassava controls. Sensitivity comparison using serial dilutions of SLCMV-infected cassava sap extracts revealed that the assay was 256-fold more sensitive than a commercial TAS-ELISA kit and 64-fold less sensitive than PCR using previously published SLCMV-specific primers. In terms of DNA content, our assay demonstrated a limit of detection of 2.21 to 4.08 × 10 ⁶ virus copies as determined by quantitative real-time PCR (qPCR). When applied to field samples (n = 490), the TAS-ELISA showed high accuracy (99.6%), specificity (100%), and sensitivity (98.2%) relative to the results obtained by the reference PCR. SLCMV infecting chaya ( Cnidoscolus aconitifolius ) and coral plant ( Jatropha multifida ) was also reported for the first time in SEA.
Conclusions
Our findings suggest that the TAS-ELISA for SLCMV detection developed in this study can serve as an attractive tool for efficient, inexpensive and high-throughput detection of SLCMV and can be applied to CMD screening of cassava stem cuttings, large-scale surveillance, and screening for resistance.
... Severe symptoms caused by mixed infections was also observed in Cameroon (Fondong et al., 2000), Cote d'Ivoire (Pita et al., 2001), Zambia (Chikoti et al., 2013), Kenya (Mwatuni et al., 2015), Tanzania and Uganda (Harrison, Zhou, Otim-Nape, Liu, & Robinson, 1997). Increased symptom severity in mixed infection is attributed to the synergistic relationship between strains of CMBs involved in the mixed infection and an increase in plant virus titre (Naseem & Winter, 2016). It is, however, important to note while symptom expression is increased in mixed infection, it is also dependent on the virus strain infecting the plant and the variety of cassava planted (Ogbe et al., 2003). ...
Cassava mosaic disease (CMD), caused by cassava mosaic begomoviruses (CMBs), is a major threat to cassava production in Nigeria. The predominant CMBs in Nigeria are African cassava mosaic virus (ACMV), East African cassava mosaic virus (EACMV) and East African cassava mosaic Cameroon virus (EACMCV), which are transmitted through infected stem cuttings and whitefly vectors. This study was conducted in 2015 and 2017 to assess the epidemiology of CMD and the current distribution of CMBs in cassava farms in South West (SW) and North Central (NC) Nigeria. A survey of cassava farms was undertaken, and samples representative of disease symptoms were collected and assessed using molecular techniques. A total of 184 and 328 cassava farms were sampled in 2015 and 2017, respectively. CMD incidence for both regions surveyed was 43.80 and 12.25% in 2015 and 2017, respectively. Fields in SW recorded a higher incidence rate in 2015 (SW: 45.11%, NC: 42.47%), while the reverse occurred in 2017 (SW: 10.90%, NC: 14.01%). Overall, the CMD incidence in Benue State (NC) was significantly higher than other locations surveyed in both years. CMD symptom severity and mean whitefly population were higher in SW Nigeria in the two survey years. ACMV was widespread across both zones, occurring in 79.1% (453/613) and 54.8% (386/704) of cassava leaf samples analysed in 2015 and 2017, respectively. EACMV was detected in only 6.0% (37/613) and 4.7% (33/704) of all cassava leaf samples analysed in 2015 and 2017, respectively. Overall, a higher proportion of infected samples were found in NC in both 2015 (NC: 85.2%, SW: 75.4%) and 2017 (NC: 73.6%, SW: 45.2%). Detection using strain‐specific primers revealed that 97% of EACMV positive samples were indeed infected by the EACMCV strain of the virus. As previously reported, samples with mixed infections showed a higher symptom severity than samples with single ACMV or EACMV infections. This study provides an update to the distribution of CMBs in SW and NC Nigeria and will be useful in development of monitoring and management strategies for the disease in both regions.
