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Introduction: Banana bunchy top disease (BBTD) caused by banana bunchy top virus (BBTV) poses a significant threat to Uganda's food and income security. Methods: To map BBTD spread and inform its management, a delimiting survey was undertaken covering the high-risk zones bordering the Democratic Republic of Congo (DR Congo) in the west, Rwanda and Tanzania in the south, and South Sudan in the north. BBTD is endemic in the DR Congo and present in Tanzania and Rwanda. The survey and environmental data were then used to map the vulnerability of Uganda's banana landscapes. Results and discussion: BBTD was only confirmed on 9% of sampled farms in north- and midwestern Uganda, with yield losses of 75% to 100%. Farmers observed BBTD over a 0.5-4.4-year period, suggesting a delayed detection. Suckers were the predominate planting materials used, increasing the risk of disease spread. Landscape suitability for BBTD was influenced by precipitation of the driest month, banana presence in 2016, land surface temperature difference (LSTD), the interaction between wind speed and LSTD, isothermality, wind speed, and the normalized difference vegetation index. These variables affect either or both the virus and aphid vector populations. Altitude did not influence the model, possibly due to disease introduction at mid to high altitudes through infected planting materials. The low-lying zones (around River Nile and Lakes Albert, Edward, and Victoria) are highly vulnerable. BBTD risk was low in northeastern Uganda with low banana production. The prediction map shows some suitable landscapes in the southwest that can expose this major banana production zone to BBTD, necessitating proactive measures. [ABSTRACT FROM AUTHOR]

Of all the plant diseases that occur in Australia, banana bunchy top disease would rank high on any list of those that have had the greatest impact on society. Bunchy top first became a major problem in Australia during World War 1 in the Tweed Valley in New South Wales, close to the border of Queensland. The Soldier Settlement Scheme was initiated to provide a livelihood for returned soldiers, and the Northern Rivers region of New South Wales was chosen as the site for a new subtropical fruit industry. Physically and psychologically damaged men were encouraged to settle on the land to grow bananas, only to be left in ruins within two years because bunchy top had destroyed their plantations. Bunchy top did not discriminate, and many other well-established growers also 'went broke'. The cries for assistance from the banana growers made it to the federal Parliament in Melbourne, and a Bunchy Top Investigation Committee was formed in 1924 with funding equally contributed by the New South Wales, Queensland, and Australian Governments. Charles Magee was the full-time plant pathologist appointed to the investigation, and he did most of the research. Most histories of the bunchy top research program follow the written accounts of Magee, but he only provided a narrow perspective. Several of the major hypotheses about the epidemiology of bunchy top disease, such as that it was spread in the plant's suckers and was vectored by the banana aphid Pentalonia nigronervosa , were established by growers such as William John (aka Jack) Burton Marks well before the Bunchy Top Investigation Committee began. This paper describes the beginnings of the subtropical banana industry, the introduction of bunchy top disease, and efforts by the scientific and farming communities to find a preventative treatment or cure for the disease. Banana bunchy top disease is the most serious viral disease of bananas in the world, and nearly wiped out the Australian banana industry in the early twentieth century. The impacts of the disease epidemic were hardest felt by veterans of World War 1, who moved to the Northern Rivers region of New South Wales to create a subtropical fruit industry as part of the Soldier Settlement Scheme. This article describes the early history of the Australian banana industry, the introduction and spread of bunchy top disease, and efforts to develop a disease management plan. Photograph by Scot C. Nelson, University of Hawaiʻi. This article belongs to the Special Issue: History of Plant Pathology in Australasia. [ABSTRACT FROM AUTHOR]

IntroductionBanana bunchy top disease (BBTD) caused by banana bunchy top virus (BBTV) poses a significant threat to Uganda’s food and income security.MethodsTo map BBTD spread and inform its management, a delimiting survey was undertaken covering the high-risk zones bordering the Democratic Republic of Congo (DR Congo) in the west, Rwanda and Tanzania in the south, and South Sudan in the north. BBTD is endemic in the DR Congo and present in Tanzania and Rwanda. The survey and environmental data were then used to map the vulnerability of Uganda’s banana landscapes.Results and discussionBBTD was only confirmed on 9% of sampled farms in north- and midwestern Uganda, with yield losses of 75% to 100%. Farmers observed BBTD over a 0.5–4.4-year period, suggesting a delayed detection. Suckers were the predominate planting materials used, increasing the risk of disease spread. Landscape suitability for BBTD was influenced by precipitation of the driest month, banana presence in 2016, land surface temperature difference (LSTD), the interaction between wind speed and LSTD, isothermality, wind speed, and the normalized difference vegetation index. These variables affect either or both the virus and aphid vector populations. Altitude did not influence the model, possibly due to disease introduction at mid to high altitudes through infected planting materials. The low-lying zones (around River Nile and Lakes Albert, Edward, and Victoria) are highly vulnerable. BBTD risk was low in northeastern Uganda with low banana production. The prediction map shows some suitable landscapes in the southwest that can expose this major banana production zone to BBTD, necessitating proactive measures.

Banana bunchy top virus is a multicomponent circular ssDNA virus (family Nanoviridae) that causes one of the most devastating diseases of cultivated bananas and plantains (family Musaceae). It is transmitted by the aphids Pentalonia nigronervosa and P. caladii among host plants of Musaceae and some other families of monocots. Our Illumina sequencing reconstruction of virome components of BBTV-infected banana plants and their neighbor non-banana plants sampled in Vietnam and Laos revealed the monocot Commelina sp. (Commelinaceae) and the dicots Bidens pilosa and Chromolaena odorata (both Asteraceae) as hosts of BBTV and circular ssDNA alphasatellites (family Alphasatellitidae). Counting the proportions and relative abundances of Illumina reads representing BBTV genome components and alphasatellites suggested that Chromolaena and Commelina are poor hosts for BBTV and one to three alphasatellite species, whereas Bidens is a permissive host for BBTV and four alphasatellite species representing two genera of Alphasatellitidae. Our findings provide evidence for the dicot plants of family Asteraceae as alternative hosts of BBTV and its alphasatellites, which warrants further investigation of these and other dicots as a potential refuge and source of BBTV and multiple alphasatellites that become associated with this virus and likely affect its replication, transmission, and host range. [ABSTRACT FROM AUTHOR]

One of the most significant banana diseases in Egypt is Banana Bunchy Top Disease, which is brought on by the Banana Bunchy Top Virus (BBTV). The creation of BBTV-free plantain seedlings from infected banana plants was the main goal of this investigation. Four separate governorates provided samples (Qalubyia, Giza, Ismailia, and Behira). All collected samples underwent BBTV testing using DAS-ELISA, which revealed that the virus infection was recorded in all inspected governorates in different ratios. The diagnostic host of BBTV was limited, infecting banana, ginger, and bird of paradise using mechanical inoculation, while only banana and ginger were infected using insect inoculation with P. nigronervosa. Polymerase chain reaction (PCR)-based detection of an amplicon from BBTV-infected banana tissues (476 bp) The multiple sequence alignment showed that EGY-Behira isolates had a high similarity of 99.7% with isolate BBTV-replicate from India. The phylogenetic tree for the BBTV-Eg Behira isolates is based on the partial nucleotide sequence alignment of the DNA-A genome. BBTV was successfully eradicated from infected plants using a combination of meristem tip culture and thermotherapy at 40 oC for two months. Virazol and Salicylic acid provided the greatest polyphenol oxidase activity (1.64 and 1.78) as well as highly enzymatic activity (2.021 and 1.96 for peroxidase). Significant biochemical changes were represented by a relative reduction in Chl a, Chl b, and carotenoid contents. It was observed that the highest reduction in chlorophyll b was 51.47%, followed by chlorophyll a+b at 51.27, chlorophyll a at 51.17, and carotenoids at -2.65, respectively. [ABSTRACT FROM AUTHOR]

Banana bunchy top disease (BBTD) is the most devasting disease of banana and plantain (Musa spp.). The disease spreads through the use of infected vegetative propagules and the banana aphid (Pentalonia nigronervosa) is the virus vector. This study seeks to understand the gender dimensions and sociocultural aspects of banana seed (vegetative propagule) sourcing and sharing practices among men and women farmers, and its influence on BBTD spread and disease control efforts. Data were collected from 300 banana farmers (187 men and 113 women) in BBTD and non-BBTD areas in southwest Nigeria. The results revealed that seed sharing within the communities is a social responsibility with members expected to share banana seed with the needy mainly as gifts rather than sold for cash. Men farmers mostly sourced seed from old fields, while women sourced seed from relatives. Harvesting of banana seed was predominantly the responsibility of men with women as helpers. Both men and women farmers in the non-BBTD area cultivated larger farm sizes and harvested more banana planting material than farmers in the BBTD area. The existing seed sourcing practices among men and women farmers heighten the risk of BBTD spread. Awareness raising on disease spread through infected seeds should consider gender-differentiated roles and social practices to reduce its spread within communities.

Banana bunchy top virus is a multicomponent circular ssDNA virus (family Nanoviridae) that causes one of the most devastating diseases of cultivated bananas and plantains (family Musaceae). It is transmitted by the aphids Pentalonia nigronervosa and P. caladii among host plants of Musaceae and some other families of monocots. Our Illumina sequencing reconstruction of virome components of BBTV-infected banana plants and their neighbor non-banana plants sampled in Vietnam and Laos revealed the monocot Commelina sp. (Commelinaceae) and the dicots Bidens pilosa and Chromolaena odorata (both Asteraceae) as hosts of BBTV and circular ssDNA alphasatellites (family Alphasatellitidae). Counting the proportions and relative abundances of Illumina reads representing BBTV genome components and alphasatellites suggested that Chromolaena and Commelina are poor hosts for BBTV and one to three alphasatellite species, whereas Bidens is a permissive host for BBTV and four alphasatellite species representing two genera of Alphasatellitidae. Our findings provide evidence for the dicot plants of family Asteraceae as alternative hosts of BBTV and its alphasatellites, which warrants further investigation of these and other dicots as a potential refuge and source of BBTV and multiple alphasatellites that become associated with this virus and likely affect its replication, transmission, and host range.

Banana bunchy top disease (BBTD), caused by a Banana Bunchy Top Virus (BBTV), is the most devastating viral disease of bananas. The genome of multipartite BBTV is about 1 Kb in size and comprises six circular single-stranded (ss) DNA components, namely DNA-R, C, S, M, U3, and N. Gene expression in multipartite DNA viruses is highly flexible due to variations in the copy number and transcript levels of individual genomic components. This enables them to adapt to changing conditions and maintain optimal fitness. In the current study, the copy number of each genetic component of BBTV and its transcript level were determined in the leaf, midrib, and root tissue of the infected banana plant. The results of the study showed that DNA copies (copies/ng) were higher in midrib (11,105 ± 10,704.42), followed by leaf (6902.91 ± 1651.14), and were lowest in root (23.49 ± 9.21) tissues. In contrast, the transcript level was highest in the root (312.45 ± 106.69) and lowest in the midrib (0.72 ± 0.16). This suggests that BBTV independently regulates the transcriptional level of each DNA component. The distribution of BBTV in different tissues assists the identification of significantly higher viral load tissues for early and sensitive disease diagnosis, which will be beneficial for better disease management. [ABSTRACT FROM AUTHOR]

Banana (and plantain, Musa spp.), in sub-Saharan Africa (SSA), is predominantly grown as a mixed crop by smallholder farmers in backyards and small farmlands, typically ranging from 0.2 ha to 3 ha. The crop is affected by several pests and diseases, including the invasive banana bunchy top virus (BBTV, genus Babuvirus), which is emerging as a major threat to banana production in SSA. The BBTV outbreak in West Africa was first recorded in the Benin Republic in 2010 and has spread to the adjoining territories of Nigeria and Togo. Regular surveillance, conducted as part of the containment efforts, requires the identification of banana fields for disease assessment. However, small and fragmented production spread across large areas poses complications for identifying all banana farms using conventional field survey methods, which is also time-consuming and expensive. In this study, we developed a remote sensing approach and machine learning (ML) models that can be used to identify banana fields for targeted BBTV surveillance. We used medium-resolution synthetic aperture radar (SAR), Sentinel 2A satellite imagery, and high-resolution RGB and multispectral aerial imagery from an unmanned aerial vehicle (UAV) to develop an operational banana mapping framework by combining the UAV, SAR, and Sentinel 2A data with the Support Vector Machine (SVM) and Random Forest (RF) machine learning algorithms. The ML algorithms performed comparatively well in classifying the land cover, with a mean overall accuracy (OA) of about 93% and a Kappa coefficient (KC) of 0.89 for the UAV data. The model using fused SAR and Sentinel 2A data gave an OA of 90% and KC of 0.86. The user accuracy (UA) and producer accuracy (PA) for the banana class were 83% and 78%, respectively. The BBTV surveillance teams used the banana mapping framework to identify banana fields in the BBTV-affected southwest Ogun state of Nigeria, which helped in detecting 17 sites with BBTV infection. These findings suggest that the prediction of banana and other crops in the heterogeneous smallholder farming systems is feasible, with the precision necessary to guide BBTV surveillance in large areas in SSA. [ABSTRACT FROM AUTHOR]

Background: Banana bunchy top virus (BBTV), cucumber mosaic virus (CMV) and banana streak virus (BSV) are important banana viruses, there are possible infections frequently with several viruses in field. Since the viruses are readily trasmitted in vegetative propagules, which pose a threat to banana production in banana-growing areas. Methods: A multiplex polymerase chain reaction (PCR) protocol combined with LiquiChip analysis to identify BSV, BBTV, and CMV, with consistent amplification of plant ubiquitin (UBQ), the banana plant messenger RNA used as a procedural control. Multiplex reverse transcription (RT)-PCR amplicons were extended by allele-specific primers, followed by hybridization with carboxylated microspheres containing unique fluorescent oligonucleotides, which were detected using the LiquiChip 200 workstation. Results: In this study, we aimed to develop a rapid, sensitive, and simultaneous detection method for BSV, BBTV, and CMV using a bead-based multiplex assay that can be applied in routine diagnosis. We demonstrated that this detection system was extremely efficient and highly specialized for differentiating individual in a mixture of viruses while being ten times more sensitive than traditional RT-PCR. The development of this method makes it feasible to detect banana viruses in field collected leaf samples. [ABSTRACT FROM AUTHOR]

Banana bunchy top virus (BBTV) causing bunchy top disease, is one of the most devastating diseases of banana and plantain. All the six genomic components of isolates from different parts of the world have been well characterised, with most of the studies focusing on replicase gene and coat protein gene. Overexpression of coat protein (CP) in Escherichia coli system can contribute significantly in structural as well as immunological studies. In the present investigation, the full length BBTV CP was cloned to pGEX-4T-2 expression vector and overexpressed in various Escherichia coli strains to obtain high quality and quantity of the CP. An augmented overexpression and stability of recombinant coat protein was achieved by molecular manipulation of the clone by restriction-free (RF) cloning platform. The RF cloning was employed to replace the thrombin cleavage site in the vector backbone, which was also present in the protein of interest, and to incorporate TEV protease site to cleave fusion protein at this specific site, and separate the affinity tag. The RF method allows direct transformation of the PCR product to undergo ligation in vivo and obtain the transformants thereby avoiding the restriction digestion and ligation of the product to the linearized plasmid. From a litre culture, 1.084 mg/ml of fusion protein with GST tag was obtained after GSH sepharose affinity column chromatography. The fluorescence spectra indicated partial disordered tertiary structure of the fusion protein. Cleavage of tag was attempted using TEV protease overexpressed and purified in the laboratory. [ABSTRACT FROM AUTHOR]

Bunchy top symptoms on banana has been reported in Bali Island since early 2011. Symptoms variation were observed in the field similar to infection of Banana bunchy top virus (BBTV). The identity of the BBTV in Bali on the basis of DNA-S nucleotide sequence has not been studied, therefore research was conducted to identify the species of BBTV infecting local banana in Bali based on sequence analysis. Research activities were initiated by collecting field samples from several local banana growing areas in Bali Island. Incidence of bunchy top disease in all locations reached 8% to 44% with disease severity ranged from 2.6% to 30%. Identification of BBTV from field samples were done by polymerase chain reaction using specific primers for BBTV (CPF/CPR) followed by sequence analysis of amplified DNA target. Specific BBTV DNA fragment was successfully amplified from 10 field samples; sequence analysis of DNA fragments showed their highest homology with BBTV. In addition the phylogenetic analysis confirmed the close relationship of BBTV isolates from Bali with various BBTV isolates from Indonesia and other isolates from the Asian group in GeneBank.

Banana aphid, Pentalonia nigronervosa Coquerel (Hemiptera: Aphididae) is known as vector of Banana bunchy top virus (BBTV) that threatening production of banana worldwide. It was reported recently that P. nigronervosa and P. caladii is “cryptic species”. A good and proper identification is necessary to verify the correct species and its status. Research was conducted to identify and to find the host range of banana aphids in Java. Aphid collection was conducted in several locations in West Java, Central Java, and East Java. Eleven morphometric characters were analyzed to assess the morphometric variations among banana aphids. Morphological identification and principle component analysis (PCA) approach were conducted for accurate identification of banana aphids. Two species of aphids were found during the survey in Java, i.e. P. nigronervosa and P. caladii. P. nigronervosa mostly infested bananas (Musa spp.), and a few was found on heliconia (Heliconia sp.) and banana traveler (Ravenala madagascariensis). In contrast, P. caladii generally infested taro (Colocasia esculenta), turmeric (Curcuma longa), costus (Costus sp.), dumbcane (Dieffenbachia sp.), but rarely on bananas.

Banana bunchy top disease (BBTD), caused by a Banana Bunchy Top Virus (BBTV), is the most devastating viral disease of bananas. The genome of multipartite BBTV is about 1 Kb in size and comprises six circular single-stranded (ss) DNA components, namely DNA-R, C, S, M, U3, and N. Gene expression in multipartite DNA viruses is highly flexible due to variations in the copy number and transcript levels of individual genomic components. This enables them to adapt to changing conditions and maintain optimal fitness. In the current study, the copy number of each genetic component of BBTV and its transcript level were determined in the leaf, midrib, and root tissue of the infected banana plant. The results of the study showed that DNA copies (copies/ng) were higher in midrib (11,105 ± 10,704.42), followed by leaf (6902.91 ± 1651.14), and were lowest in root (23.49 ± 9.21) tissues. In contrast, the transcript level was highest in the root (312.45 ± 106.69) and lowest in the midrib (0.72 ± 0.16). This suggests that BBTV independently regulates the transcriptional level of each DNA component. The distribution of BBTV in different tissues assists the identification of significantly higher viral load tissues for early and sensitive disease diagnosis, which will be beneficial for better disease management.

Abstract Background The genome of Banana bunchy top virus (BBTV) consists of at least six circular, single-stranded DNA components of ~ 1 kb in length. Some BBTV isolates may also carry satellite DNA molecules that are not essential for BBTV infection. The relation between multipartite DNA virus replication and their transcriptional levels and the underlying mechanism remain unclear. Results To understand the coordinated replication and transcription of the multiple genomic components, the absolute amounts of each BBTV DNA component were measured by real-time PCR (qPCR), and their transcriptional levels were determined by RNAseq and reverse transcription-qPCR (qRT-PCR). Significant differences were found in the absolute amounts of individual BBTV genomic components. Transcriptional levels of each BBTV genomic component obtained from the RNAseq data matched closely to those obtained from qRT-PCR, but did not correspond to the absolute amount of each DNA component. The ratio of transcript over DNA copies ranged from 46.21 to 1059.44%, which was possibly regulated by the promoter region in the intergenic region of each component. To further determine this speculation, the promoter region of the DNA-S, −M or -N was constructed to the upstream of green fluorescent protein (GFP) gene for transient expression by agrobacterium-mediated transformation method. The qRT-PCR showed the highest transcriptional activity was promoted by DNA-N promoter, about 386.58% activity comparing with CaMV 35S promoter. Confocal microscopy observation showed that the intensity of green fluorescence was corresponding to that of qRT-PCR. Conclusions Our data clearly showed that BBTV was able to control the transcriptional level of each DNA component independently by through the promoter sequences in the intergenic region. Moreover, a cis-acting element from DNA-N component had a high transcriptional activity.

Abstract Banana bunchy top disease (BBTD) is one of the world's most destructive viral diseases of banana and plantain, causing up to 100% yield loss in severe cases. The disease is vectored by banana aphids (Pentalonia nigronervosa) and carried long distances through the movement of infected plant materials. The banana aphids harboring banana bunchy top virus (BBTV) present in banana producing regions are the sole vector and the most efficient method of transmitting the virus to the healthy plants. Controlling the spread of BBTD has been very challenging since no known banana germplasm is immune to BBTV. The disease can be managed with the use of virus‐free planting material and roguing. However, once BBTD is established in the field, it is very difficult to eradicate or manage it. Therefore, a more sustainable way of controlling the disease is developing host plant resistance against the virus and the vector. Biotechnological strategies via RNA interference (RNAi) could be used to target the banana aphid as well as BBTV to reduce virus‐associated yield losses of banana and plantain, which feed over 500 million people around the world. This review discusses the status of BBTD and perspectives on effective RNAi technologies for controlling BBTV and the vector, banana aphid, transmitting the virus as sustainable management of the disease.

The removal of infected individuals is a common practice in the management of plant disease outbreaks. It minimizes the contact between healthy individuals and inoculum sources by reducing the infectious window of contaminated individuals. This requires early detection and consistent removal at landscape scale. Roguing of mats with symptoms of banana bunchy top disease (BBTD) in Cavendish banana production systems has been tested in Australia, using trained personnel, but has never been tested in smallholder systems. We studied the effectiveness of long‐term consistent roguing in prolonging the productivity of banana orchards under smallholder farming systems in highland banana and plantain dominated production systems in Africa. We assessed the possibility of low‐risk seed sourcing from the managed plots. Roguing reduced BBTD incidence to 2% in managed farmer fields and to 10% in experimental field plots, while a nonmanaged field eventually collapsed in the same period. With roguing, new infections decreased monthly compared to an exponential increase in a nonmanaged field. The emergence of new infections in both managed and nonmanaged farms followed a seasonal cycle. BBTD managed plots were a source of low‐risk seed for replacing the rogued mats in the same fields, but perhaps not safe for use in nonendemic areas. We conclude that it is possible for smallholder farmers to recover and maintain banana productivity with rigorous roguing, which would entail early identification of symptoms and early removal of diseased mats. Studies are needed on the intensity of roguing under different disease and production conditions. [ABSTRACT FROM AUTHOR]

Banana bunchy top disease (BBTD) is one of the world's most destructive viral diseases of banana and plantain, causing up to 100% yield loss in severe cases. The disease is vectored by banana aphids (Pentalonia nigronervosa) and carried long distances through the movement of infected plant materials. The banana aphids harboring banana bunchy top virus (BBTV) present in banana producing regions are the sole vector and the most efficient method of transmitting the virus to the healthy plants. Controlling the spread of BBTD has been very challenging since no known banana germplasm is immune to BBTV. The disease can be managed with the use of virus‐free planting material and roguing. However, once BBTD is established in the field, it is very difficult to eradicate or manage it. Therefore, a more sustainable way of controlling the disease is developing host plant resistance against the virus and the vector. Biotechnological strategies via RNA interference (RNAi) could be used to target the banana aphid as well as BBTV to reduce virus‐associated yield losses of banana and plantain, which feed over 500 million people around the world. This review discusses the status of BBTD and perspectives on effective RNAi technologies for controlling BBTV and the vector, banana aphid, transmitting the virus as sustainable management of the disease. [ABSTRACT FROM AUTHOR]

Polyclonal antibodies against abaca bunchy top virus (ABTV) and banana bunchy top virus (BBTV) proteins are necessary for immuno-based detection of these two viruses in abaca (Musa textilis Nee). In this study, recombinant bunchy top viral coat proteins fused with a 6xHis tag at the N-terminus were expressed in E. coli BL21StarTM(DE3)pLysS strain and purified under denaturing conditions. Purified recombinant ABTV and BBTV coat proteins were used as antigens for the production of rabbit polyclonal antibodies. IgG was purified and evaluated by Direct Antigen Coating (DAC)-ELISA and further optimized by testing primary to secondary antibody dilution combinations. Analysis of ABTV and BBTV-infected abaca samples using the optimized DAC-ELISA assay showed that the anti-ABTV CP IgG can react to BBTV and that anti-BBTV CP IgG can react to ABTV, hence, a cross-reaction. The study demonstrates the advantage of using recombinant DNA technology for mass production of antigens for antibody production. Although specificity of the polyclonal antibodies may have been compromised when renatured recombinant proteins were used as immunogens, the ability of the purified IgGs to detect positive abaca samples reveals that the DAC-ELISA can be routinely used for screening disease-free abaca planting materials. [ABSTRACT FROM AUTHOR]

Autonomously replicating alphasatellites (family Alphasatellitidae) are frequently associated with plant single-stranded (ss)DNA viruses of the families Geminiviridae, Metaxyviridae, and Nanoviridae. Alphasatellites encode a single replication-initiator protein (Rep) similar to Rep proteins of helper viruses and depend on helper viruses for encapsidation, movement, and transmission. Costs versus benefits of alphasatellite-helper virus association are poorly understood. Our surveys in Southeast Asia (SEA) for wild and cultivated banana plants infected with banana bunchy top virus (BBTV, Nanoviridae) and Illumina sequencing reconstruction of their viromes revealed, in addition to a six-component BBTV genome, one to three distinct alphasatellites present in sixteen of twenty-four BBTV-infected plants. Comparative nucleotide and Rep protein sequence analyses classified these alphasatellites into four distinct species: two known species falling into the genus Muscarsatellite (subfamily Petromoalphasatellitinae) previously identified in SEA and two novel species falling into the tentative genus Banaphisatellite (subfamily Nanoalphasatellitinae) so far containing a single species recently identified in Africa. The banaphisatellites were found to be most related to members of the genus Fabenesatellite of subfamily Nanoalphasatellitinae and the genus Gosmusatellite of subfamily Geminialphasatellitinae, both infecting dicots. This suggests a dicot origin of banaphisatellites that got independently associated with distinct strains of monocot-infecting BBTV in Africa and SEA. Analysis of conserved sequence motifs in the common regions driving replication and gene expression of alphasatellites and BBTV strains revealed both differences and similarities, pointing at their ongoing co-evolution. An impact of alphasatellites on BBTV infection and evasion of RNA interference-based antiviral defences was evaluated by measuring relative abundance of BBTV genome components and alphasatellites and by profiling BBTV- and alphasatellite-derived small interfering RNAs. Taken together, our findings shed new light on the provenance of alphasatellites, their co-evolution with helper viruses, and potential mutual benefits of their association., Competing Interests: The authors declare no competing interests., (© The Author(s) 2024. Published by Oxford University Press.)

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Banana bunchy top virus (BBTV), one of the most devastating viruses of banana, is transmitted by the banana aphid, Pentalonia nigronervosa. The high degree of morphological similarity between P. nigronervosa and the related experimental vector P. caladii makes it difficult to distinguish the two species. DNA barcoding can be used as an alternative for the rapid identification of these aphid species. However, standard molecular identification techniques for small insects usually require maceration of the sample to obtain sufficient amounts of DNA, resulting in the loss of voucher specimens. In this study, a non-destructive DNA extraction method for aphids was optimised, allowing the specimens to remain intact for use as vouchers for further morphological studies. Sufficient DNA concentrations were obtained from the aphid extractions and were used for species identification through direct sequencing of PCR products. Extracted DNA was further used to detect BBTV in the insect vector, P. nigronervosa. Approximately 78% of the aphids collected from symptomatic plants in infected plantations in KwaZulu-Natal tested positive for BBTV, as well as some aphids collected in other African countries. The BBTV viral strain identified from South Africa grouped with the "South Pacific" clade. This non-destructive DNA extraction method can be used in an early detection management strategy, especially in epidemiology and virus-vector studies of Banana bunchy top disease (BBTD). [ABSTRACT FROM AUTHOR]

Rhizospheric and endophytic bacteria isolated from the roots and corms of banana were tested to find out their efficiency in controlling against banana bunchy top virus (BBTV). Bioformulations of mixtures of endophytic Bacillus pumilus and B. subtilis isolated from banana cv. Grand Naine and rhizobacterial isolate Pseudomonas fluorescens (Pf1) were found to be effective in increasing the growth and physiological parameters such as pseudostem girth and height, number of leaves, phyllochron, and leaf area in biohardened plants under greenhouse study. The consortia of bioformulation mixture of B. pumilus, B. subtilis, and P. fluorescens I showed 61.62% disease reduction over control. The defence enzymes such as peroxidase (POX), polyphenol oxidase (PPO), phenylalanine ammonia lyase (PAL), and total phenol were induced to an elevated level in biohardened plants. The applications of bioformulations to plants led to delay the symptom expression for 63.75 to 70.50 days compared to control after challenge inoculation with the virus in 34-67% of plants that exhibited the symptoms till 150 DAI. However, biohardening of plants with the same combinations of bacteria three days after BBTV inoculation led to express the symptoms 29.16 to 36.71 days and there was a significant decrease in plant growth parameters. Biopriming prior to BBTV infection has attributed to the enhanced plant growth and resistance against BBTV whereas, the same treatments after virus inoculation did not induce resistance. This study has proved that the time of application of consortia of bio-inoculants determines their effect of induced resistance to BBTV in micropropagated plants. [ABSTRACT FROM AUTHOR]

Pentalonia nigronervosa Coquerel (Hemiptera: Aphididae) is the only known vector of Banana bunchy top virus (BBTV). The objective of this research was to study the preference and suitability of banana aphid P. nigronervosa to various banana genotypes. Survey conducted at Talang Betutu, South Sumatra indicates the existence of different preferences of the P. nigronervosa toward different varieties in the field. Host suitability test was conducted using 13 banana varieties that were invested with P. nigronervosa from taro plants. Preference test was conducted using a 200 cm x 200 cm x 150 cm mesh cage that were used to house 13 banana genotypes that were invested with P. nigronerosa. The numbers of aphids on different banana genotypes were observed. Result of the study showed that “kepok” genotype was more suitable for the growth of P. nigronervosa compared to other genotypes. The suitability was shown by higher population, faster population growth, lower mortality and the higher proportion of alate adults. Banana kepok infested with 20 aphids at the beginning of the test reached 324 individuals within 24 days with population growth rate of 8.27% per day, and produced 1.9% of alate imagoes appeared 6 days after infestation. Host preference test using the same genotypes suggested that the aphid prefer banana kepok more than to any other genotypes.

Banana bunchy top disease (BBTD) is caused by banana bunchy top virus (BBTV), the most important virus affecting banana. Currently, no cultivar or accession of banana has complete resistance to BBTD. A total of 36 wild Musa spp. accessions, including 34 Musa balbisiana and 2 M. acuminata subsp. errans ("Agutay"), were screened for resistance against BBTV. In greenhouse tests using viruliferous banana aphids (Pentalonia nigronervosa ), all M. balbisiana accessions remained symptomless, and BBTV was not detected in any of these plants by PCR at 3 and 6 months postinoculation. In contrast, 100% disease incidence was recorded in M. acuminata subsp. errans and in cv. Lakatan susceptible control plants. The PCR-negative M. balbisiana plants were then transferred to a field with high BBTV inoculum pressure where they remained symptomless and PCR-negative for up to 5 years, while all cv. Lakatan developed BBTD. Wild M. balbisiana accessions showed a high level of resistance and possibly immunity to BBTV and are expected to provide a resource for conventional and marker-assisted breeding.[Formula: see text] Copyright © 2023 The Author(s). This is an open access article distributed under the CC BY-NC-ND 4.0 International license., Competing Interests: The author(s) declare no conflict of interest.

The Banana Bunchy Top Virus (Genus: Babuvirus) reduces plant growth and prevents banana production. Because of the very large number of properties with banana plants in South East Queensland, Australia, a mapping approach was developed to delineate individual and clusters of banana plants to help plant identification and enable prioritization of plant inspections for Banana Bunchy Top Virus. Due to current outbreaks in South East Queensland, there are concerns that the virus may spread to the major banana growing districts further north. The mapping approach developed was based on very high spatial resolution airborne orthophotos. Object-based image analysis was used to: (1) detect banana plants using edge and line detection approaches; (2) produce accurate and realistic outlines around classified banana plants; and (3) evaluate the mapping results. The mapping approach was developed based on 10 image tiles of 1 km × 1 km and was applied to orthophotos (3600 image tiles) from September 2011 covering the entire Sunshine Coast Region in South East Queensland. Based on field inspections of the classified maps, a user’s mapping accuracy of 88% (n = 146) was achieved. The results will facilitate the detection of banana plants and increase the inspection rate of Banana Bunchy Top Virus in the future.

Banana bunchy top virus (BBTV) affects all varieties of banana plants and causes heavy economic loss in most of the banana cultivating areas. The BBTV genome comprises of six DNA components; in this study, we have cloned the six BBTV-DNA components from one of the BBTV-infected plants (Tri-8) and were submitted to GenBank. Analysis of the BBTV DNA-R component showed that it belonged to south Pacific group. Resistance against BBTV has not been observed so far in banana plants and removal and killing of the infected plants has been routinely practiced. Hence, early detection of BBTV infection would be desirable and various detection methods routinely employed include enzyme linked immunosorbent assay (antigen-antibody based) and molecular-based methods such as polymerase chain reaction (PCR), qPCR, or LAMP PCR. Most of these methods require enzymes or antibodies for detection and hence are expensive. Here, we report a visual detection method (AuNP probe assay) using gold nanoparticles (AuNPs) functionalized with an ssDNA-thiolated probe (CR1). This method is based on the hybridization of the functionalized AuNPs with the target DNA (BBTV). In the AuNP probe assay, the functionalized AuNPs retains red colour when BBTV DNA is present, and in the absence of BBTV DNA, the colour of the functionalized AuNPs changes to purple when salt is added. The AuNP probe assay was compared with PCR for the detection of banana plants and it was found that AuNP probe assay was better than PCR in detecting BBTV infection (86.5% for AuNP probe assay and 65% for PCR). The AuNP probe assay was found to be highly specific to BBTV and was found to detect up to 1 pg/μl of the plasmid (pTZBBTri 4, BBTV DNA) mixed with healthy banana DNA. [ABSTRACT FROM AUTHOR]

Banana bunchy top disease (BBTD) can be caused by the infection of two different viruses, Banana bunchy top virus (BBTV) or Abaca bunchy top virus (ABTV). Both viruses can be transmitted persistently by aphid Pentalonia nigronervosa Coq. The research was conducted to detect and to differentiate the virus bypolymerase chain reaction-restriction fragment length polymorphism (PCRRFLP) techniques. Infected plants were collected from Yogyakarta (Sleman, Yogyakarta city, Bantul, Gunung Kidul, and KulonProgo). Nucleon Phytopure DNA Extraction Kit method was used to extract the total DNA of infected plants. Universal primers of Common DNA region (S-CRF and S-CRR) and specific primers DNA-R (C1-CRF and CI-CRR) were used for PCR amplification. PCR products were analyzed by RFLP technique using the restriction enzyme of DraI. The results reconfirm previous reports that bunchy top disease of banana in Yogyakarta is caused by BBTV. The ABTV was not detected in this present study. Based on the RFLP analysis it was concluded that BBTV collected in this study could be divided into three groups. Group 1 consisted of BBTV isolate from Sleman and Yogyakarta city with two fragments DNA of 400 and 388 bp. Group 2 consisted of isolate BBTV from Kulon Progo and Gunung Kidul with three fragments DNA of 400, 388, and 323 bp. Group 3 consisted of isolate from Bantul with two fragments DNA of 723 and 376 bp. Further study on the complete characteristics of these groups is still needed. Penyakit kerdil pisang dapat disebabkan oleh infeksi virus yang berbeda yaitu Banana bunchy top virus(BBTV) atau Abaca bunchy top virus (ABTV). Kedua virus tersebut ditularkan secara persisten oleh kutu daun Pentalonia nigronervosa Coq. Penelitian ini bertujuan untuk mendeteksi dan membedakan virus dengan polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP).Tanaman terinfeksi dikoleksi dari Yogyakarta (Sleman,Kota Yogyakarta, Bantul, Gunung Kidul, dan Kulon Progo). Metode Phytopure DNA Extraction Kit dan CTAB digunakan untuk mengisolasi DNA total. Primer universal Common DNA region (S-CRF/S-CRR) dan primer spesifik DNA-R BBTV(C1-CRF danCI-CRR) digunakan dalam amplifikasi dengan PCR. Produk PCRBBTV dianalisis dengan teknik RFLP menggunakan enzim restriksi Dra I. Hasil penelitian memperkuat laporan sebelumnya bahwa penyakit kerdil pisang di Yogyakarta disebabkan oleh BBTV, dan belum ditemukan ABTV. Berdasarkan analisis RFLP, BBTV dapat dibedakan menjadi tiga kelompok. Kelompok 1 yaitu BBTV isolat Sleman dan Kota Yogyakarta dengan dua fragmen DNA berukuran sekitar 400 dan 388 bp. Kelompok 2 yaituBBTV isolat Kulon Progo dan Gunung Kidul dengan tiga fragmen DNA berukuran sekitar 400, 388, dan 323 bp. Kelompok 3 yaitu BBTV isolat Bantul dengan dua fragmen DNA berukuran sekitar 723 dan 376 bp. Penelitian tentang karakterisasi dari ketiga kelompok tersebut masih diperlukan.