Banana bunchy top virus

Diseased suckers are the main source of primary infection. Acquisition of the virus by the banana aphid requires about 18 hours of feeding and then the aphid can retain the virus for approximately two weeks.

The retransmission of this virus can happen after as little as two hours of feeding on a healthy plant however it takes about a month for the BBTD symptoms to appear after infection.

To infect, the carrier aphid can feed on the banana plant for as few as 15 minutes, but more often a couple hours, as the longer feeding time will increase the odds of transmission. The suckers produced on infected plants that would usually be used for planting the next season will also be diseased, which is one way the disease can spread from year to year.

Banana aphids also have the capability to feed on Heliconias and flowering ginger; however, these alternate hosts of the aphid vector are not hosts of the virus. The ability of banana aphids to feed on alternate hosts is important to keep in mind when attempting to control the virus.

Copyright Privacy Policy Contact Us. Bunchy Top of Banana. Disease cycle of Banana. Page actions. Banana bunchy top virus Banana bunchy top virus. Investigation on the Bunchy Top Disease of the Banana. Purification of banana bunchy top virus BBTV. Fruits 44 2 Virus-like particles associated with banana bunchy top disease contain small single-stranded DNA. If you are currently working at destroying BBTV infected plants and associated banana aphids on your property and find another infected plant, then you do not need to notify the Department.

However, if your plantation has been free of BBTV for some time, after an old detection and notification to the Department, and you find BBTV again on your property then you need to notify the Department.

How do I source healthy planting material? Advice on how to source healthy planting material can be found in the Banana Industry Biosecurity Code of Practice at abgc. Can I move bananas out of the Control Zone? Yes, you can move banana fruit out of the zone, but not banana plants. Why do I need to destroy the banana aphids on infected plants before I destroy the plants?

The banana aphids on infected plants may carry BBTV and will fly away to other plants if the infected plant they are on is destroyed. Destroying the aphids first reduces the risk of heathy plants becoming infected with BBTV.

How do I destroy the banana aphids and infected banana plants? More topics in this section. Destroying infected plants and aphids. Proliferating tissue cultures initiated from meristems from BBTV-infected plants were also shown to produce virus-free plants Helliot et al.

Subsequently, it was reported that the uneven distribution and low concentration of BBTV after exposure of proliferating tissue cultures to heat leads to BBTV-free primordial cells, which in turn develop into healthy plants Wu and Su, Susceptible Musa species include M. However, differences in susceptibility between cultivars subject to either experimental or field infection have frequently been noted Magee, ; Muharam, ; Espino et al.

Espino et al. However, low levels of infection as assessed by symptom expression or total absence of symptoms following aphid inoculation was noted in some cultivars containing the B genome. These included 'Radja' AAB, syn. These cultivars were not back-indexed by aphid transmission to a susceptible banana cultivar or tested biochemically for example, by ELISA , so the presence of symptomless infection cannot be ruled out.

Also, greater numbers of aphids than the 15 used here may have resulted in infection. Nevertheless, it appears that real differences exist in cultivar reaction to bunchy top and the time taken before symptoms are expressed. Cultivars within the Cavendish subgroup form the basis of the international banana export trade and are generally highly susceptible to bunchy top. However, it appears that not all cultivars with an AAA genome are similarly susceptible.

Symptoms are also slower to develop and are less severe Ngatat et al. These factors may contribute to a reduced rate of aphid transmission and field spread in plantations of 'Gros Michel' Ngatat et al. There is no evidence for hosts outside the Musaceae, though reports have been conflicting. Su et al. However, Hu et al. Magee was unable to infect Strelitzia sp. Since the advent of improved and reliable diagnostics for BBTV, searches for alternative hosts outside the Musaceae, including those earlier suspects, have turned out to be negative.

Primary hosts are banana cultivars derived from M. Plants can become infected at any stage of growth and there are some initial differences between the symptoms produced in aphid-infected plants and those grown from infected planting material. In aphid-inoculated plants, symptoms usually appear in the second leaf to emerge after inoculation and consist of a few dark-green streaks or dots on the minor veins on the lower portion of the lamina.

The streaks form 'hooks' as they enter the midrib and are best seen from the underside of the leaf in transmitted light.

The 'dot-dash' symptoms can sometimes also be seen on the petiole. The following leaf may display whitish streaks along the secondary veins when it is still rolled. These streaks become dark green as the leaf unfurls.

Successive leaves become smaller, both in length and in width of the lamina, and often have chlorotic, upturned margins. The leaves become dry and brittle and stand more erect than normal giving the plant a rosetted and 'bunchy top' appearance. Suckers from an infected stool can show severe symptoms in the first leaf to emerge. The leaves are rosetted and small with very chlorotic margins that tend to turn necrotic.

Dark-green streaks are usually evident in the leaves. Infected plants rarely produce a fruit bunch after infection and do not fruit in subsequent years. Plants infected late in the growing cycle may fruit once, but the bunch stalk and the fruit will be small and distorted.

On plants infected very late, the only symptoms present may be a few dark green streaks on the tips of the flower bracts Thomas et al. Mild strains of BBTV, which induce only limited vein clearing and dark-green flecks, and symptomless strains have been reported in Cavendish plants from Taiwan Su et al. Mild disease symptoms are expressed in some banana cultivars and Musa species. The dark-green leaf and petiole streaks, so diagnostic and characteristic of infection of cultivars in the Cavendish subgroup, can be rare or absent Magee, Some plants of 'Veimama' AAA, Cavendish subgroup , after initial severe symptoms, have been observed to recover and to display few if any symptoms.

BBTV is transmitted by an aphid vector Pentalonia nigronervosa and is disseminated in vegetative planting material, but is not transmitted by mechanical inoculation Magee, Magee showed that banana bunchy top was systemic. Following aphid inoculation, symptoms generally do not appear until a further two or more leaves have been produced Magee, This period can vary between 19 days in summer to days in winter Allen, a.

The virus can only be acquired by aphids from the first symptom leaf or those formed subsequently Magee, Suckers produced on an infected stool generally develop severe symptoms before reaching maturity Magee, The emergence of virus-free suckers from an infected stool due to incomplete virus systemicity in the corm has been reported Djailo et al.

Magee also concluded that the virus was restricted to the phloem tissue. Microscopic examination revealed hypertrophy and hyperplasia of the phloem tissue and a reduction in the development of the fibrous sclerenchyma sheaths surrounding the vascular bundles. The cells surrounding the phloem contained abnormally large numbers of chloroplasts giving rise to the macroscopic dark-green streak symptom.

Trace levels of virus were eventually detected by PCR in leaves formed prior to inoculation, but replication was not demonstrated. This latter observation is consistent with the inability to transmit the virus by aphids from such leaves Magee, and with the sequential development of single, new leaves from the basal meristem.

Vegetative Propagation BBTV is efficiently disseminated in conventional planting material including corms, bits and suckers. All suckers from an infected stool will eventually become infected Djailo et al. BBTV is also transmitted in micropropagated banana plants Drew et al. From time to time, apparently virus-free meristems producing apparently virus-free plants can arise from an infected clone Thomas et al. Plantations established from infected suckers and corms were completely unproductive.

Epidemiology of Banana Bunchy Top The epidemiology of banana bunchy top in Australia, as well as in sub-Saharan Africa, is simplified by the presence of a single susceptible host and a single vector species P. Dissemination over long distances is by infected planting material and it is by this means that new plantings in isolated areas usually become infected. Spread over short distances from these infection foci is by the banana aphid Kumar et al.

In studies of outbreaks of bunchy top in commercial banana plantations, Allen b, showed that the average distance of secondary spread of the disease by aphids was only On average, the interval between infection of a plant and movement of aphids from this plant to initiate new infections elsewhere the disease latent period was equivalent to the time taken for 3.

The rate of leaf emergence varied seasonally with a maximum in summer Allen, On the basis of these studies, a computer program has been developed which simulates epidemics of bunchy top RN Allen, Brisbane, , personal communication.

This program, which is commercially available, allows epidemiological factors to be varied and their effect on the progess of the epidemic and disease control to be monitored. In the Philippines, Opina and Milloren also demonstrated that most new infections were adjacent to or in close proximity to primary sources of infection. In Malawi, the spread of BBTV within the country was attributed to human movement of planting material and cultural practices Kumar et al. Inadvertent multiplication and distribution of infected planting material by government and non-governmental programmes and the movement of infected suckers by migrant workers and refugees are thought to be the major factor for the spread of BBTV in sub-Saharan Africa Kumar et al.

In Australia, the banana aphid Pentalonia nigronervosa was considered to have a role in the etiology of banana bunchy top Darnell-Smith, and in was conclusively demonstrated to be the vector Magee, Banana aphids have a worldwide distribution with a host range that includes Musa textilis and other species in the Musaceae.

Species in several closely related plant families including the Araceae Alocasia sp. However, a degree of host preference is displayed and some difficulty can be experienced transferring them between host species.

Recently, mitochondrial COI sequence based analysis identified lineages on most of the non- Musa hosts as Pentalonia caladii Foottit et al.

A recent population genetics study of Pentalonia aphids using mitochondrial COI or microsatellite markers found that P. Aphids were found 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 Robson et al.

Aphid numbers decrease during periods of drought Wardlaw, The transmission parameters reported from Hawaii Hu et al. Similar parameters have also been reported by Thiribhuvanamala et al. Colonies of P. Banana plants treated with systemic herbicide can serve as source for virus acquisition for up to 6 weeks after treatment Hooks et al.

Devastating epidemics occurred in Fiji at the turn of the century and in Australia in the s. The economic effect in northern New South Wales was dramatic. In recent years, bunchy top disease has been decimating the banana industry in Pakistan. BBTV is a major constraint to production in many areas where it occurs. Precise estimates of losses due to BBTV are not known.

However, Cook et al. This study suggests significant economic benefit in controlling BBTV. Prior to , the only assays available for banana bunchy top were visual assessment of symptoms and aphid transmission to a sensitive banana cultivar. Subsequently, both serological and nucleic acid-based assays have become available.

All isolates tested from Africa, Australia, Asia and the Pacific region are serologically related Thomas, Due to the variable regulations around de registration of pesticides, your national list of registered pesticides or relevant authority should be consulted to determine which products are legally allowed for use in your country when considering chemical control. Pesticides should always be used in a lawful manner, consistent with the product's label. Regulatory Control BBTV has not been eradicated from any country where it occurs, but it is believed to have been eliminated from certain banana-growing districts in Australia.

Here, the disease is kept in check by strict State Government legislation which controls the source and movement of planting material, controls the issue of planting permits and requires the destruction of feral plants and all plants with symptoms. Banana inspectors are also employed to police these regulations and locate diseased and feral plants.

An ambitious programme of eradication is on-going which is based on replacing plantations where the disease regularly occurs, with BBTV-tested, tissue-cultured, planting material Thomas et al. Host-Plant Resistance When little work had been undertaken on testing germplasm for resistance, it was thought that all cultivars were susceptible, although some may take longer to develop symptoms and others may escape infection because of aphid preferences or host morphological factors.

S everal studies have since been undertaken to evaluate Musa genotypes for BBTV resistance and found genotypes with tolerance no symptoms and near normal performance of virus infected plants e. Gros Michel , delayed expression of symptoms e. Dwarf Apple, also known as Santa Catarina and difficult to infect e. Fugamou Espino et al. Cultural Control Banana bunchy top disease can be effectively controlled by the eradication of diseased plants and the use of virus-tested planting material.

Before destruction, diseased plants should first be sprayed with power kerosene or insecticide to kill all viruliferous aphids. The whole stool, including corm and all associated suckers, must then be destroyed by uprooting and chopping into small pieces or by herbicide treatment, as the virus will ultimately spread to all parts of the mat.

Control must be practised across the whole production area to avoid the rapid re-infection of virus-tested planting material Thomas et al. Chemical Control Aphicides have been used in some countries to control populations of Pentalonia nigronervosa , the aphid vector of bunchy top, and a decrease in disease incidence has been reported.

In Tonga, Aphidius colemani , a parasitic wasp, has been released in an attempt at biological control of the aphid vector, but its effects on disease incidence have been disappointing. First report of Banana bunchy top virus in banana and plantain Musa spp. Plant Disease, 97 2 Allen RN, Epidemiological factors influencing the success of roguing for the control of bunchy top disease of bananas in New South Wales.

Australian Journal of Agricultural Research, 29 3 Spread of bunchy top disease in established banana plantations. Australian Journal of Agricultural Research, 29 6 Further studies on epidemiological factors influencing control of banana bunchy top disease and evaluation of control measures by computer simulation.

Australian Journal of Agricultural Research, 38 2 The spread of bunchy top disease between banana plantations in the Tweed River District during Almeida, R. Spread of an introduced vector-borne banana virus in Hawaii. Molecular Ecology, 18 1 , Identification and characterization of a distinct banana bunchy top virus isolate of Pacific-Indian Oceans group from North-East India. Virus Research, Anceau C, Identification and characterisation of viruses associated to the syndrome of banana bunchy top disease BBTD.

Final Scientific Report, March to February Anhalt, M. Effect of temperature, vector life stage, and plant access period on transmission of Banana bunchy top virus to banana. Phytopathology, 98 6 , APPPC, Insect pests of economic significance affecting major crops of the countries in Asia and the Pacific region.

Technical Document No. First report of Banana bunchy top virus infecting banana in Iran. Plant Pathology, 56 4 Journal of General Virology, 78 1 ; 33 ref. Blomme, G. A historical overview of the appearance and spread of Musa pests and pathogens on the African continent: highlighting the importance of clean Musa planting materials and quarantine measures.

Annals of Applied Biology, 1 , Bryce G, The bunchy top plantain disease.