Bunchy Top Disease Research Articles

Effect of banana bunchy top virus infection on morphology and growth characteristics of banana

AbstractField experiments were conducted in Oahu, Hawaii, to investigate the effects of banana bunchy top virus (BBTV) infection on growth and morphology of banana (Musa acuminata). The time interval between aphid inoculation of BBTV and the initial appearance of disease symptoms (i.e. incubation period) was also determined. Plants infected with BBTV showed a significant reduction in petiole size (i.e. length and distance), plant canopy and height, leaf area, pseudostem diameter and chlorophyll content compared with control plants. Growth differences between virus‐infected and control plants were not observed until 40–50 days after the plants were inoculated with viruliferous aphids. Other growth parameters such as petiole width and leaf production were not statistically different between infected and control plants. The incubation period of banana bunchy top disease or appearance of symptoms ranged from 25 to 85 days after aphid inoculation. However, PCR assays provided earlier detection of BBTV in banana plants compared with visual symptoms.

Biohardening with Plant Growth Promoting Rhizosphere and Endophytic bacteria induces systemic resistance against Banana bunchy top virus

Tissue culture banana has emerged as one of the leading global agro based industrial technologies. However, the banana plants are found to be more susceptible to pests and diseases due to their pliable nature and lack of withstanding in the natural environment. Banana bunchy top disease (BBTD) caused by Banana bunchy top virus (BBTV) is the most serious virus disease of banana and plantain world wide. Biopriming (or) biohardening refers to treatment of tissue culture banana plantlets with microbial inoculants to strengthen the plantlets against biotic and abiotic stresses. Forty plant growth promoting endophytic bacteria (PGPE) were isolated from the corm and roots of banana and tested for the ability to induce systemic resistance against BBTV. Phenotypic and molecular characterization of the endophytic bacteria revealed the presence of Pseudomonas and Bacillus species. Micropropagated banana plantlets were tested for the presence of BBTV by ELISA, DIBA and PCR and the uninfected plants were biohardened with two rhizobacterial ( Pseudomonas fluorescens, Pf1, CHA0) and endophytic bacterial (EPB5, EPB22) strains. Plants treated with mixtures of rhizobacterial and endophytic bacterial formulations viz., EPB5 + EPB22 + Pf1 + CHA0 was significantly effective in reducing BBTV under field conditions recording 33.33% infection with 60% reduction over control. The expression of defense-related enzymes and pathogenesis related proteins were more in the plants treated with rhizosphere and endophytic bacterial formulations than the control plants. The morphological and physiological characters were also well pronounced in the treated plants indicating its plant growth promoting nature. Thus, the present study clearly demonstrated that PGPR and PGPE mediated induction of systemic resistance in banana plants against BBTV have the potential role in the management of BBTD.

Effect of imidacloprid foliar treatment and banana leaf age on Pentalonia nigronervosa (Hemiptera, Aphididae) survival

Pentalonia nigronervosa, the banana aphid, is the vector of Banana bunchy top virus to banana. This virus is the etiological agent of banana bunchy top disease, a limiting factor in many banana growing regions, including Hawaii, United States. Laboratory bioassays on banana plants were conducted to evaluate the efficacy of imidacloprid (Provado®), to control P. nigronervosa by comparing insect mortality at four different insecticide concentrations (120,60,24, and 12 ppm) over 1 month, and compared effects on the aphids on new emerging, and old leaf material. We found significant differences between treatments and time after treatment. Aphids survived poorly on newer plant growth, regardless of presence or absence of imidacloprid, or time after treatment. Examining the insecticidal effect on old leaves only, we found that the three highest concentration treatments resulted in high mortality over the 4‐week‐long period of testing. Our results confirm that imidacloprid foliar application on bananas results in effective control of aphids and does not become systemic within the plant. From these results, it is likely that management of banana aphid using imidacloprid under field conditions will be effective on old leaves and new leaves that are sprayed, but leaves emerging after sprays will not be completely protected from aphids. Regular scouting for aphids should be implemented in support of imidacloprid applications.

Molecular characterisation of Banana bunchy top virus (BBTV) from Pakistan

Banana bunchy top disease is caused by a single-stranded circular DNA virus, banana bunchy top virus (BBTV), which is a member of the genus Babuvirus (family Nanoviridae). We have cloned and sequenced five components (DNA-R, DNA-S, DNA-N, DNA-M and DNA-C) of a BBTV isolate originating from Pakistan. In addition, the DNA-R and several other components of five further isolates, originating from geographically distinct sites across the banana-growing area of Sindh province, Pakistan, were cloned and sequenced. Analysis of the sequences indicates that BBTV present in Pakistan belongs to the "South Pacific" group of isolates and that the genetic diversity of the virus in the country is very low. The virus shows the highest levels of sequence identity to BBTV isolates originating from Egypt, India and Australia. The significance of these results with respect to the possible origin of the virus in Pakistan and the prospects for obtaining genetically engineered resistance to the virus are discussed.

Induction of systemic resistance in banana (Musa spp.) against Banana bunchy top virus (BBTV) by combining chitin with root-colonizing Pseudomonas fluorescens strain CHA0

Pseudomonas fluorescens strains CHA0 and Pf1 were investigated for their biocontrol efficacy against Banana bunchy top virus (BBTV) in banana (Musa spp.) alone and in combination with chitin under glasshouse and field conditions. Bioformulation of P. fluorescens strain CHA0 with chitin was effective in reducing the banana bunchy top disease (BBTD) incidence in banana under glasshouse and field conditions. In addition to disease control, the bioformulation increased the economic yield significantly compared to the untreated control. Increased accumulation of oxidative enzymes, peroxidase (PO), polyphenol oxidase (PPO), phenylalanine ammonia lyase (PAL), pathogenesis-related (PR) proteins, chitinase, β-1,3-glucanase and phenolics were observed in CHA0 bioformulation amended with chitin-treated plants challenged with BBTV under glasshouse conditions. Indirect ELISA indicated the reduction in viral antigen concentration in P. fluorescens strain CHA0 with chitin-treated banana plants corresponding to reduced disease ratings. The present study revealed that induction of defence enzymes by P. fluorescens with chitin amendment reduced the BBTD incidence and increased bunch yield in banana.

Potential implications of biopriming in banana (Musa spp) plantlets against banana bunchy top virus (BBTV)

Transplant media as a means for the introduction of biological agents is currently being investigated in a variety of crops. This study aimed to investigate the impact of microbial inoculation in micropropagated banana plantlets to enhance their resistance against Banana bunchy top virus (BBTV). Virus indexed micropropagated plantlets of banana were subjected to root colonization followed by foliar spraying with bacterial strains Pseudomonas fluorescens Pf1, CHA0 and Bacillus subtilis EPB22 during primary and secondary hardening stage in the nursery, at the time of repotting and 3 months after planting in the pot. Microbe inoculated plantlets showed enhanced PR proteins and defense enzymes besides reducing banana bunchy top disease incidence under glasshouse condition. The results indicated the effective use of beneficial microbes in reducing the disease incidence of BBTV in tissue culture banana plantlets. In addition, the molecular characterization of endophytes isolated from banana plantlets, using SDS-PAGE and RAPD-PCR revealed that endophytes were categorized into two distinct groups. These results emphasize the significance of microorganisms in protection of young plantlets from transplanting stresses in field. Further, the use of beneficial microorganisms instead of chemicals sustains an ecological niche in the agricultural ecosystem.

First report of Banana bunchy top virus infecting banana in Iran

Banana bunchy top disease is one of the most serious diseases of bananas (Musa spp.) worldwide. The disease is caused by Banana bunchy top virus (BBTV), the type species of the Babuvirus genus; (family Nanoviridae). The genome of BBTV is comprised of at least six circular single-stranded DNA (ssDNA) components, each approximately 1 Kb in size. Symptoms of BBTV infection include plant stunting, foliar yellowing and most characteristically, dark green streaks on the pseudostem, petioles and leaves (Harding et al. 1993; Vetten et al., 2005). From 2004 to 2006, a series of field surveys were conducted in the major banana-growing areas in Iran: Mazandaran province (Sari, Babol, Behshahr, and Ghaemshahr) in the north and Hormozgan province (Jask and Varz-Abad) in the south. A total of 164 banana plant samples with bunchy top, stunting and leaf samples with green streak symptoms were collected. Samples were tested for the presence of BBTV with a double-antibody sandwich enzyme-linked immunosorbent assay (DAS-ELISA) using positive control and polyclonal antibodies against BBTV, according to the supplier's instructions (Bio-Rad). Of the samples tested, 27 were positive for BBTV using DAS-ELISA. To confirm BBTV identification, polymerase chain reaction (PCR) was carried out using samples that previously tested positive by ELISA. Forward [F3: 5′-GGAAGAAGCCTCTCATCTGCTTCAGAGAR C-3′; nts 287 to 258] and reverse [FPCR4: 5′-TTCCCAGGCGCACACCTTGAGAAACGA AAG-3′; nts 284 to 313] primers were used to amplify complete BBTV DNA-1 (Furuya et al., 2005). PCR analysis showed fragments of approximately 1 Kb in 19 samples. Furthermore, using primer pairs designed to differentiate BBTV strains (Su et al., 2003), Iranian BBTV isolates were divided into two distinct strains. This is the first report of the occurrence of BBTV in Iran.

Screening banana plants for banana bunchy top virus with primers specific to Indian isolates

The banana bunchy top disease is a serious threat to banana production. Caused by a DNA virus, its detection using specific primers is the only sensitive method to certify mother plants for tissue culture. Newer strains and variants of this virus were reported based on severity of symptoms and difference in the sizes of amplicons in a PCR assay. A search for newer strains or variants of this virus was therefore attempted in this study. We designed primers unique to the stem-loop region of DNA 2 from clones of this virus occurring in Indian Musa spp. These and other primers obtained from the literature were used to screen plants in the field and tissue cultured propagules. The results presented here report the occurrence of at least two distinct strains showing variation in sequences of DNA 2. The likely origin of this variant sequence is discussed here.

Cytopathology, Mode of Aphid Transmission and Search for the Casual Agent of Cotton Bunchy Top Disease

AbstractThe cytopathological effects of cotton bunchy top (CBT) disease and its mode of transmission by Aphis gossypii Glover (cotton aphid), were studied. CBT infection affected the leaf epidermal layer producing a loose, ruptured and rough surface morphology with many stomata closed and misshapen. Roots of CBT‐infected plants showed reduced growth, small knots and a dark brown appearance. A single aphid per plant was capable of transmitting CBT at 5%, whereas three aphids per plant transmitted CBT to 50% of the cotton seedlings and 20 aphids per plant transmitted the disease agent to 80% of the cotton seedlings. Aphis gossypii acquired CBT after a minimum acquisition access period of 5 min and transmitted the agent after a minimum inoculation access period of 1 h. Both alate and apterous aphids and nymph instars 2, 3 and 4 of A. gossypii transmitted CBT. This preliminary data suggest that A. gossypii transmits CBT in a semi‐persistent manner. Myzus persicae Sulz (green peach aphid) was unable to transmit CBT. A comprehensive attempt to isolate the CBT agent, using a range of virological techniques including double‐stranded RNA extraction, two‐dimensional gel electrophoresis for viroid, circular DNA test, nanovirus polymerase chain reaction (PCR), luteovirus PCR and enzyme‐linked immunosorbent assay, phytoplasma test, nucleoprotein purification and electron microscopy, was unsuccessful, raising the possibility that CBT may be caused by a unique new pathogen.

Biology of <I>Pentalonia nigronervosa</I> (Hemiptera, Aphididae) on Banana Using Different Rearing Methods

The banana aphid, Pentalonia nigronervosa Coquerel, is present worldwide where banana (Musa spp.) is grown. It is the vector of Banana bunchy top virus (Nanoviridae, Babuvirus), the etiological agent of banana bunchy top disease, currently the most important constraint for banana producers in Hawaii. P. nigronervosa is not well studied, and effects of temperature on its growth and reproduction are unknown. We studied the longevity and fecundity of one clone of banana aphid on different types of plant materials to determine an effective method to study the insect in the laboratory. We found that insects performed better unconfined on plantlets, followed by leaf midrib cuttings. We also conducted complete life table studies with P. nigronervosa on banana leaf midrib cuttings at 20, 25, and 30 degrees C, with a photoperiod of 12:12. Intrinsic rate of increase (r), net reproductive rate (R0), doubling time (DT), nymphal mortality, and mean offspring per female all showed maximal rates at 25 degrees C. Population growth was studied on whole banana plantlets as well, and growth rates were also highest at 25 degrees C. We found r to be greater when aphids were reared on intact banana plantlets than on cuttings. Our results show the importance of comparing insect rearing methods for studies such as life tables.

Rhizosphere and endophytic bacteria for induction of systemic resistance of banana plantlets against bunchy top virus

Bunchy top is one of the most important viral diseases affecting banana production worldwide. Several approaches have been made to control or combat the bunchy top virus disease in banana, transmitted by the banana aphid, Pentalonia nigronervosa Coq. No tactic is able to completely protect the plants against this viral infection. To ameliorate this problem, an attempt was made to use different bacterial strains, which could be inoculated to the roots of micropropagated plantlets to avoid the post transplanting problems. Virus indexed micropropagated plantlets of banana cv. Virupakshi (AAB) were subjected to root colonization followed by foliar spraying with three bacterial strains viz ., Pseudomonas fluorescens strains Pf1, CHA0 and Bacillus subtilis strain EPB22 along with an un-inoculated control during primary and secondary hardening stage in the nursery and at the time of transplanting, 3rd, 5th and 7th month after planting in the field. Microbe inoculated plantlets showed improved vegetative growth, physiological attributes, PR—proteins and phenol contents besides reducing banana bunchy top disease (BBTD) incidence in the field. These results indicate that, transplant mixes amended with beneficial bacterial strains can enhance growth of banana plants, besides reducing the damage caused by banana bunchy top virus.

Within-Plant Distribution and Binomial Sampling of Pentalonia nigronervosa (Hemiptera: Aphididae) on Banana

The banana aphid, Pentalonia nigronervosa Coquerel (Hemiptera: Aphididae), infests banana (Musa spp.) worldwide. Pentalonia nigronervosa is the vector of Banana bunchy top virus (family Nanoviridae, genus Babuvirus) the etiological agent of Banana bunchy top disease (BBTD). BBTD is currently the most serious problem affecting banana in Hawaii. Despite the importance of this vector species, little is known about its biology or ecology. There are also no sampling plans available for P. nigronervosa. We conducted field surveys to develop a sampling plan for this pest. Ten plots were surveyed on seven commercial banana farms on the island of Oahu, HI, for the presence of P. nigronervosa on banana plantlets. We found aphids more frequently near the base of plants, followed by the newest unfurled leaf at the top of the plant. Aphids were least likely to be located on leaves in between the top and bottom of the plant. Aphid infestation on surveyed plots ranged from 8 to 95%. We developed a sequential binomial sampling plan based on our surveys. We also discovered that the within-plant distribution of P. nigronervosa is an important factor to consider when sampling for this pest. Our sampling plan will assist in the development of sustainable management practices for banana production.

Within-Plant Distribution and Binomial Sampling of <I>Pentalonia nigronervosa</I> (Hemiptera: Aphididae) on Banana

The banana aphid, Pentalonia nigronervosa Coquerel (Hemiptera: Aphididae), infests banana (Musa spp.) worldwide. Pentalonia nigronervosa is the vector of Banana bunchy top virus (family Nanoviridae, genus Babuvirus) the etiological agent of Banana bunchy top disease (BBTD). BBTD is currently the most serious problem affecting banana in Hawaii. Despite the importance of this vector species, little is known about its biology or ecology. There are also no sampling plans available for P. nigronervosa. We conducted field surveys to develop a sampling plan for this pest. Ten plots were surveyed on seven commercial banana farms on the island of Oahu, HI, for the presence of P. nigronervosa on banana plantlets. We found aphids more frequently near the base of plants, followed by the newest unfurled leaf at the top of the plant. Aphids were least likely to be located on leaves in between the top and bottom of the plant. Aphid infestation on surveyed plots ranged from 8 to 95%. We developed a sequential binomial sampling plan based on our surveys. We also discovered that the within-plant distribution of P. nigronervosa is an important factor to consider when sampling for this pest. Our sampling plan will assist in the development of sustainable management practices for banana production.

Characterization and genetic status of Banana bunchy top virus isolated from Okinawa, Japan

Isolates of Banana bunchy top virus (BBTV), which causes bunchy top disease in bananas, were collected in field surveys on seven islands in Okinawa Prefecture, Japan. From 44 banana samples, one isolate from each island was selected, and the DNA-1 and DNA-3 components were sequenced. Analysis of the major common region of DNA-1 showed that BBTV in Okinawa belongs to the Asian group of BBTV. DNA-1 and DNA-3 analysis revealed that Okinawan BBTV had a closer relationship with isolates from Taiwan and the Philippines than with some isolates from China and Vietnam. All the Okinawan BBTV isolates had high homology in the nucleotide sequences of DNA-1 and DNA-3 (%) because of a single, recent BBTV invasion of this area.

A PCR-Based Method, With Internal Control, for the Detection of <I>Banana Bunchy Top Virus</I> in Banana

Banana bunchy top disease is a major constraint to banana production in most regions where this crop is grown. The disease is caused by Banana bunchy top virus (BBTV), a multicomponent, single-stranded DNA virus of the family Nanoviridae. We have designed primers to a conserved region of the master replication-associated protein that are useful for the polymerase chain reaction (PCR)-mediated detection of BBTV. In addition, primers to banana genomic sequence are used as an internal control, overcoming the uncertainty (owing to false-negatives) inherent in PCR diagnostics. Together these primer sets are a valuable tool in the effort to control BBTV, particularly in screening micropropagated banana plantlets for the absence of virus before release to farmers.

Occurrence and Incidence of Banana Bunchy Top Disease in Southern Part of Sindh

Occurrence and Incidence of Banana Bunchy Top Disease in Southern Part of Sindh

Specificity of Host-pathogen Interaction of Banana Bunchy Top Disease

Specificity of Host-pathogen Interaction of Banana Bunchy Top Disease

Banana bunchy top nanovirus DNA-1 encodes the 'master' replication initiation protein.

Banana bunchy top nanovirus has a multicomponent, circular single-stranded DNA genome comprising at least six integral components, BBTV DNA-1 to -6, which have been consistently associated with bunchy top disease worldwide. At least three other components, BBTV S1, S2 and Y, which have been isolated from Taiwanese BBTV isolates, do not appear to be integral components. We show here that both BBTV DNA-1 and S1, which encode replication initiation (Rep) proteins, were capable of self-replication when bombarded into banana embryogenic cell suspensions. However, only BBTV DNA-1 was capable of directing the replication of two other BBTV genomic components, namely BBTV DNA-3 which encodes the coat protein, and DNA-5 which encodes a retinoblastoma binding-like protein. These results indicate that (i) BBTV DNA-1 is the minimal replicative unit of BBTV and encodes the 'master' viral Rep and (ii) BBTV S1 is possibly a satellite DNA which is unable to replicate integral BBTV components.

First record of banana bunchy top disease in New Caledonia

Banana bunchy top disease was identified for the first time in New Caledonia in June 1999. The disease was found only on the south part of the main island, mainly in residential areas and infrequently in commercial banana plantations. Infected plants showed obvious, typical symptoms and an eradication campaign is being undertaken.

Quantitative epidemiology of Banana Bunchy Top Virus Disease and its control

Models of a banana bunchy top virus disease epidemic were developed to incorporate the two key features of an epidemic in a plantation in the Philippines: an exponential increase in disease incidence over 10 years, and a declining gradient of incidence from the outside edge of the plantation to the centre. A non‐spatial model consisted of three difference equations to describe the numbers of latently infected and of infectious plants in the plantation and the size of the inoculum source outside the plantation. In a spatial model the outside portion of the plantation was divided into eight blocks running parallel to the outside edge. The dispersal gradient of the inoculum was assumed to be negative exponential. Analysis of the two models showed that for disease incidence to increase exponentially over time, the rate of disease progress could be dependent either on internal spread and roguing rate (proportion of diseased plants removed and replaced per unit time) or on the rate of increase of external inoculum pressure. The observed incidence gradient from the edge to the centre of the plot could be explained only if external inoculum dominated the parameters in the spatial model. This model was also used to explore a variable roguing rate across blocks. Simulations indicated that this may produce small gains over the adoption of a constant roguing rate over all blocks, but was risky because a shift of roguing emphasis only slightly too far towards the outside blocks can result in a dramatic increase in disease.