Bunchy Top Disease Research Articles

Identification of phytoplasmas associated with Bunchy Top disease of papaya in Colima, Mexico

Phytoplasmas, rickettsiae and viruses have been detected in papaya plants with Bunchy Top disease (BT). In 2019, papaya plants with BT-like symptoms were observed in agroecosystems of Colima, Mexico. In order to determine the BT-associated phytoplasmas species or subgroups, asymptomatic and symptomatic plants were collected from papaya agroecosystems in four papaya producer municipalities, as well as papaya-associated weeds and insects. Phytoplasma detection and identification was conducted by PCR, sequencing and phylogenetics of translocase subunit SecA (secA) and 16S ribosomal RNA (16Sr) genes, and PCR-RFLPs in vitro and in silico for 16Sr gene. In papaya, phytoplasma groups 16SrI (subgroup AF), 16SrX, and 16SrXIII were identified in 2.08% (4 out of 192) symptomatic samples. The results of RFLPs in silico analysis showing the presence of 16SrX and 16SrXIII (sub)groups. In papaya-associated weeds and insects, phytoplasmas of group 16SrI (subgroups AF and B) were identified in 1.7% (3 out of 174) and 1.1% (2 out of 185) evaluated samples, respectively. Phytoplasma-carrying weeds were Amaranthus palmeri and Echinochloa colona; positive insects were Micrutalis calva and Balclutha mexicana. It is the first time that phytoplasmas 16SrI-AF, 16SrX y 16SrXIII are associated with Bunchy Top disease of papaya in agroecosystems from Colima, Mexico. Phytoplasmas 16SrX y 16SrXIII are first reported in papaya plants at the world level and in Mexico, respectively. Phytoplasma-carrying weeds and insects are new records as natural reservoirs and potential vectors.

The role of insect vector Pentalonia nigronervosa in spreading banana bunchy top disease in South Sumatera

Banana (Musa spp.) is widely cultivated by the people of South Sumatra. Banana Bunchy Top disease is caused by Banana bunchy top virus (BBTV), which is transmitted by the vector Pentalonia nigronervosa Coquerel (Hemiptera: Aphididae) and asymptomatic banana used for propagation. This study aimed to investigate the role of P. nigronervosa. in determining the distribution pattern of this disease in South Sumatra. The research used survey methods in several districts and cities in South Sumatra, namely Ogan Ilir, Ogan Komering Ilir, OKU East, OKU South, OKU Induk, Palembamg, Prabumulih, Banyuasin, Musi Banyuasin, and Lubuk Linggau. Samples were taken using purposive sampling method if BBTV-infected bananas in an area. The results showed P. nigronervosa was only found in Ogan Ilir and OKU Induk districts, but in fact this disease was spread in 10 districts and cities. A total of 14 banana cultivars in South Sumatera were infected by BBTV transmitted by P. nigronervosa, namely Mas, Cavendish, Putri, Lilin, Nangka, Ambon, Udang, Barangan, Kepok, Gedah, Rottan, Raja, Kapas and Raja Nangka. The highest banana population and percentage of banana plants infested by BBTV was found in the Ogan Ilir district in Mas and Lilin cultivars.

The untold history of banana bunchy top disease

The untold history of banana bunchy top disease

Comparative RNA-seq analysis of resistant and susceptible banana genotypes reveals molecular mechanisms in response to banana bunchy top virus (BBTV) infection

Bananas hold significant economic importance as an agricultural commodity, serving as a primary livelihood source, a favorite fruit, and a staple crop in various regions across the world. However, Banana bunchy top disease (BBTD), which is caused by banana bunchy top virus (BBTV), poses a considerable threat to banana cultivation. To understand the resistance mechanism and the interplay of host suitability factors in the presence of BBTV, we conducted RNA-seq-based comparative transcriptomics analysis on mock-inoculated and BBTV-inoculated samples from resistant (wild Musa balbisiana) and susceptible (Musa acuminata ‘Lakatan’) genotypes. We observed common patterns of expression for 62 differentially expressed genes (DEGs) in both genotypes, which represent the typical defense response of bananas to BBTV. Furthermore, we identified 99 DEGs exclusive to the 'Lakatan' banana cultivar, offering insights into the host factors and susceptibility mechanisms that facilitate successful BBTV infection. In parallel, we identified 151 DEGs unique to the wild M. balbisiana, shedding light on the multifaceted mechanisms of BBTV resistance, involving processes such as secondary metabolite biosynthesis, cell wall modification, and pathogen perception. Notably, our validation efforts via RT-qPCR confirmed the up-regulation of the glucuronoxylan 4-O-methyltransferase gene (14.28 fold-change increase), implicated in xylan modification and degradation. Furthermore, our experiments highlighted the potential recruitment of host's substrate adaptor ADO (30.31 fold-change increase) by BBTV, which may play a role in enhancing banana susceptibility to the viral pathogen. The DEGs identified in this work can be used as basis in designing associated gene markers for the precise integration of resistance genes in marker-assisted breeding programs. Furthermore, the findings can be applied to develop genome-edited banana cultivars targeting the resistance and susceptibility genes, thus developing novel cultivars that are resilient to important diseases.

The aphid Pentalonia nigronervosa (Hemiptera: Aphididae) takes advantage from the quality change in banana plant associated with Banana bunchy top virus infection.

Viral diseases can change plant metabolism, with potential impacts on the quality of the plant's food supply for insect pests, including virus vectors. The banana aphid, Pentalonia nigronervosa Coquerel, is the vector of the Banana bunchy top virus (BBTV), the causal agent of Banana bunchy top disease (BBTD), the most devastating viral disease of bananas in the world. The effect of BBTV on the life-history traits and population dynamics of P. nigronervosa remains poorly understood. We therefore studied the survival rate, longevity, daily fecundity per aphid, tibia length, population growth, and winged morph production of a P. nigronervosa clone grown on healthy or infected, dessert, or plantain banana plants. We found that daily fecundity was higher on infected banana than on healthy banana plants (plantain and dessert), and on plantain than on dessert banana plants (healthy and infected). Survival and longevity were lower on infected dessert bananas than on other types of bananas. In addition, virus infection resulted in a decrease in aphid hind tibia length on both plant genotypes. The survival and fecundity table revealed that the aphid net reproduction rate (Ro) was highest on plantains (especially infected plantain), and the intrinsic growth rate (r) was highest on infected plants. Finally, the increase of aphids and alate production was faster first on infected plantain, then on healthy plantain, and lower on dessert banana (infected and uninfected). Our results reinforce the idea of indirect and plant genotype-dependent manipulation of P. nigronervosa by the BBTV.

Resistance of Musa balbisiana accessions of the Philippines to banana bunchy top virus.

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 two 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 three and six months post inoculation. 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 theyremained symptomless and PCR-negative for up to five years, while all cv. Lakatan developed BBTD. Wild M. balbisiana accessions showed a high level of resistance, possibly immunity, to BBTV and are expected to provide a resource for conventional and marker assisted breeding.

First report of Banana bunchy top disease (BBTD) on Banana (Saba variety) in Cagayan Valley Region, Philippines

First report of Banana bunchy top disease (BBTD) on Banana (Saba variety) in Cagayan Valley Region, Philippines

Banana bunchy top disease in Africa—Predicting continent‐wide disease risks by combining survey data and expert knowledge

AbstractAcross Africa, banana bunchy top disease (BBTD) severely impacts banana production and livelihoods of millions of smallholder farmers. Mapping vulnerability of landscapes to monitor BBTD establishment and spread is crucial for proactive measures of disease exclusion. To highlight current and future risks of BBTD in Africa, the relationship between 1160 field observations from 14 BBTD surveys and environmental covariate maps was determined using logistic regression. From these relationships, we inferred the environmental suitability of the African landscape for the possible wider spread of BBTD. Using this information and expert knowledge, we generated a map highlighting the main banana production areas at risk of BBTD entry and establishment. We combined these maps to create a priority map that highlights the areas that need most attention in combating BBTD through surveillance and measures to prevent its spread. Our analysis shows that BBTD is widespread across tropical Africa, with dispersal over several hotspots. Central and Western Africa are most favourable for the development of BBTD. Central, West and South‐East Africa are most at risk of BBTD entry and initial establishment. Areas in West and Central Africa, in the Great Lakes Region in Eastern Africa and in South‐East Africa, particularly in Malawi and Mozambique, score high on the prioritization index for surveillance and mitigation efforts. Recent reports of BBTD presence in north‐western Uganda and western Tanzania support these risk predictions. For these and other not‐yet‐infected areas, measures for close surveillance and proactive management of the disease are needed.

An aphid transmitted banana bunchy top disease of banana and its detection: A Review

One of the most significant horticultural crops in the world, the banana is an edible fruit (technically a berry) produced by a variety of large herbaceous flowering plants in the genus Musa. It is grown in about 120 different countries around the world. Particularly, virus intensification between subsequent plantings via contaminated planting material limits the banana crop yield. Banana bunchy top virus (BBTV) control is challenging because it spreads vegetatively (through suckers or in vitro plantlets) and by an aphid Pentalonia nigronervosa Coquerel, thus increasing the virus potential for dispersal within the fields. To propagate plants, exchange germplasm, breed better genotypes, and distribute them are challenging to use planting material that has been virus affected. Diagnosis of the BBTV, relies essentially only upon the symptom’s recognition of infection and, seldom, with additional affirmation by aphid transmission. At present, polymerase chain reaction (PCR) based and non-PCR techniques are available for BBTV detection. Implementation of these diagnostic tools and procedure facilitates the identification of healthy ones of the germplasm that can be used in propagation systems.

Variation in Symptom Development and Infectivity of Banana Bunchy Top Disease among Four Cultivars of Musa sp.

Banana bunchy top disease (BBTD) is an invasive viral disease spreading in Africa. It is transmitted by banana aphids and infected planting material, causing production losses. Clean seeds and timely eradication of diseased plants are effective tools in BBTD management. These depend on timely disease detection. We assessed the relationship between symptom expression and infectivity of the virus in four cultivars of banana. Plantlets from four cultivars, ‘FHIA 25’; ‘Aloga’; ‘Ebenga’ and ‘Sotoumon’, were exposed to viruliferous aphids and monitored for symptom expression. They were also tested as sources for virus transmission fortnightly by allowing non-viruliferous aphids acquisition access prior to transfer to healthy test plants. The time required to show symptoms and the symptom expression were compared, and infection tested by PCR. Disease expression varied from four weeks in ‘FHIA 25’ to fifteen in ‘Sotoumon’. Only the symptomatic leaves tested positive and could act as infection sources. Overall, ‘FHIA 25’ was the most susceptible cultivar, while ‘Sotoumon’ was the least susceptible and most rapidly expressive of BBTD, yet there was no difference in the leaf emergence rate between the cultivars. These results present important aspects of BBTD control and the safety of planting materials that should be tested in the field.

Tools for the management of the banana bunchy top disease in small holder systems

Tools for the management of the banana bunchy top disease in small holder systems

Influence of altitude as a proxy for temperature on key Musa pests and diseases in watershed areas of Burundi and Rwanda

Pests and diseases are key biotic constraints limiting banana production among smallholder farmers in Eastern and Central Africa. Climate changemay favour pest and disease development and further exacerbate the vulnerability of smallholder farming systems to biotic constraints. Information on effects of climate change on pests and pathogens of banana is required by policy makers and researchers in designing control strategies and adaptation plans. Since altitude is inversely related to temperature, this study used the occurrence of key banana pests and diseases along an altitude gradient as a proxy for the potential impact of changes in temperature associated with global warming on pests and diseases. We assessed the occurrence of banana pests and diseases in 93 banana fields across three altitude ranges in Burundi and 99 fields distributed in two altitude ranges in Rwanda watersheds. Incidence and prevalence of Banana Bunchy Top Disease (BBTD) and Fusarium wilt (FW) was significantly associated with temperature and altitude in Burundi, revealing that increasing temperatures may lead to upward movement of banana diseases. No significant associations with temperature and altitude were observed for weevils, nematodes and Xanthomonas wilt of banana (BXW). Data collected in this study provides a baseline to verify and guide modelling work to predict future pest and disease distribution according to climate change scenarios. Such information is useful in informing policy makers and designing appropriate management strategies.

The Influence of Soil Nutrients Availability on Banana Bunchy Top Disease Incidence in Banyumas Regency, Central Java Province, Indonesia

The banana bunchy top is one of the important diseases on bananas, presumably coupled with the influence of soil properties, despite no fixed information regarding their relationship. Therefore, this study aims to map the soil nutrient contents at some banana plantation center and determine the effect of nutrient availability on the incidence of banana bunchy top disease (BBTD). This study set a purposive sampling according to the banana cultivation distribution to gain soil samples and data on BBTD incidence. Soil samples were analyzed for macronutrient content, including N capacity using the Kjeldahl method, Bray method for P analysis, and CH<sub>4</sub>OAc methods for K analysis. According to the investigation, the range of total N was 0.2% to 0.75%, showing BBTD incidence from 5.8% to 9.47%, respectively. In line with the total P, BBTD incidence increased from 8.03% to 9.62% in the P content of 15 to 35 ppm. In contrast, in the total K of 0.5 to 1 cmol(+) kg<sup>-1</sup>, the BBTD incidence tended to decline from 9.68% to 9%. It was concluded that BBTD incidence would increase with the higher levels of N and P but decrease with the higher K. In Banyumas Regency, BBTD incidence increased in the altitude range of 100 to 300 m above sea level, then decreased at a higher altitude. BBTD incidence also exhibited an unstable response to pH changes. Bunchy top disease incidence was the highest between pH 5 and 8. This could be a guide to soil management to reduce BBTD incidences.

Quantitation of Multipartite Banana Bunchy Top Virus Genomic Components and Their Transcripts in Infected Tissues of Banana (Musa acuminata)

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.

Banana Mapping in Heterogenous Smallholder Farming Systems Using High-Resolution Remote Sensing Imagery and Machine Learning Models with Implications for Banana Bunchy Top Disease Surveillance

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.

Identification of suitable internal control genes for gene expression analysis of banana in response to BBTV infection

Banana is one of the most abundant crops produced annually in the Philippines. The presence of banana bunchy top virus (BBTV) leading to banana bunchy top disease is one of the factors hindering the continuous production of the fruit crop. The use of an appropriate and stable internal control gene as reference in validation of differentially-expressed genes in an organism is important. This study aims to identify appropriate internal control genes for differential gene expression analysis in Musa balbisiana and Musa acuminata specific for BBTV infection. RNA extraction, complementary DNA (cDNA) synthesis and RT-qPCR (quantitative real time polymerase chain reaction) of BBTV-resistant and BBTV-susceptible Musa genotypes were performed. The RT-qPCR quantification data were then subjected to analysis on RefFinder software and geomean ranking values were calculated along with the four statistical algorithms (delta Cq, Genorm, BestKeeper and NormFinder). Based on the comprehensive ranking values in the software, L2 gene was the most suitable internal control gene for the differential expression analysis of both BBTV-resistant and BBTV-susceptible banana accessions. The internal control gene is recommended for the validation of selected candidate resistance and host factor genes in response to BBTV infection.

BIOLOGY OF Pentalonia nigronervosa COQUEREL ON VARIOUS ZINGIBERACEOUS CROPS

Pentalonia nigronervosa Coquerel (Hemiptera; Aphididae) is the main vector of banana bunchy top disease caused by Banana Bunchy Top Virus (BBTV). The disease is an important and most damaging disease to the crop because infected bananas fail to produce fruits. As the vector of BBTV, P. nigronervosa is able to lives not only on banana plants but also on others plants, especially those belong to Family Zingiberaceae. The objective of this research was to reveal the biology of P. nigronervosa on banana and other plant species belong to Family Zingiberaceae commonly found around banana cultivation areas. The research was conducted in the Laboratory of Entomology, Department of Plant Protection, Faculty of Agriculture, Sriwijaya University from June to December 2021. The research was an experimental research arranged in a Completely Randomized Design using plant species as treatment and was replicated 10 times of replications. Young suckers of banana and zingiberaceous plants were used to rear the banana aphid where all biological aspects of the aphid were observed. P. nigronervosa and the young suckers were placed in a transparent pot covered with transparent plastic with a window made from cheese cloth to facilitate air movement. Room temperature was set to approximately 25oC since the aphid grow and reproduce well under such temperature. The results showed that P. nigronervosa are able to live and reproduce not only on banana but also on seven species of Zingiberaceous plants with little variation of some morphological and biological parameters. The significant different was found between biological characteristics of the aphid lived on torch ginger and cardamom which had longer life cycle but smaller fecundity compared to other experimental hosts used in the research.

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Banana seed exchange networks in Burundi – Linking formal and informal systems

Seed system network analysis can reveal exchange connections between stakeholders and test scenarios such as those of seed systems shocks. We investigated the seed exchange network structure, disease surveillance risk, and gender contribution in Burundi, under two banana disease risk scenarios. Two sites where banana bunchy top disease (BBTD) is endemic in Cibitoke Province were compared with a site free of the disease in Gitega Province. All sites had formal seed interventions using community nurseries. A quantitative survey on seed sharing was done followed by a qualitative evaluation through focus group discussions. Banana seed sourcing options were fewer in the disease-free site, which also had higher cultivar diversity. Most farmers sourced seed informally within a three-kilometer radius. Seed sharing within and between villages was based on social and family linkages, especially for women. The interaction between the formal system and informal seed exchange was more active where new cultivars, or better seed quality was expected. The BBTD endemic region had lower seed quality assessment stringency. Farmers used both direct mother plant assessment and seed source reputation in seed evaluation. The formal banana seed systems are sources of new varieties, and trusted for clean seed but the informal system was still used as a main source of seed, especially local cultivars. Assessing disease surveillance scenarios shows women in a weaker position for healthy seed acquisition. Identifying the roles of individuals in seed systems can support decision processes for seed interventions in vegetatively propagated crops.

Musa Germplasm A and B Genomic Composition Differentially Affects Their Susceptibility to Banana Bunchy Top Virus and Its Aphid Vector, Pentalonia nigronervosa.

Banana bunchy top disease (BBTD), caused by the banana bunchy top virus (BBTV, genus Babuvirus), is the most destructive viral disease of banana and plantain (Musa spp.). The virus is transmitted persistently by the banana aphid, Pentalonia nigronervosa Coquerel (Hemiptera: Aphididae). While research efforts have focused on screening Musa genotypes for BBTD resistance, comparatively little work has been carried out to identify resistance to banana aphids. This study assessed 44 Musa germplasm of different A and B genome composition for the performance of banana aphids under semicontrolled environmental screenhouse conditions and in a field trial established in a BBTD endemic location. In the screenhouse, the AA diploid Calcutta 4 had the lowest apterous aphid density per plant (9.7 ± 4.6) compared with AAB triploid Waema, which had the highest aphid densities (395.6 ± 20.8). In the field, the highest apterous aphid density per plant (29.2 ± 6.7) occurred on the AAB triploid Batard and the lowest (0.4 ± 0.2) on the AA diploid Pisang Tongat. The AA diploid Tapo was highly susceptible to BBTD (100% infection) compared with the genotypes Balonkawe (ABB), PITA 21 (AAB), Calcutta 4 (AA), and Balbisiana Los Banos (BB), which remained uninfected. The Musa genotypes with apparent resistance to BBTD and least susceptibility to aphid population growth provide options for considering aphid and BBTD resistance in banana and plantain breeding programs.