BXW stands for the Banana Xanthomonas Wilt and describes a disease of Banana popularly known as Xanthomonas Wilt (BXW), or banana bacterial wilt (BBW) or enset wilt is a bacterial disease caused by Xanthomonas campestris pv.musacearum. After being originally identified on a close relative of banana, Ensete ventricosum, in Ethiopia in the 1960s, BXW emanated in Uganda in 2001 affecting all types of banana cultivars. Since then BXW has been diagnosed in Central and East Africa including banana growing regions of: Rwanda,Democratic Republic of the Congo, Tanzania, Kenya, Burundi, and Uganda
BXW symptoms can be sorted into two domains: symptoms on the inflorescence and symptoms on the fruit. Symptoms on the fruit are usually used to distinguish BXW from alternative banana diseases. A bacterial ooze is excreted from the plant organs and this is a mandatory sign that BXW may be present. Common symptoms on the fruit include internal discoloration and premature ripening of the fruit. A cross section of the BXW infected banana is characterized by the yellow- orange discoloration of the vascular bundles and dark brown tissue scaring. Symptoms on the inflorescence include a gradual wilting and yellowing of the leaves plus wilting of the bracts and shriveling of the male buds. Many factors may affect the combination of disease symptoms on show. These include the particular cultivar infected, how the disease has been transmitted and the current growing season.
BXW is transmitted in any one of the following ways;
Soil is one of the main sources for Xanthomonas campestris pv. musacearum inoculum. Xanthomonas campestris pv. musacearum may contaminate the soil for four months and more. BXW awareness campaigns have helped reduce the numbers of farmers growing bananas on contaminated plantains aiding in the control of the disease overall. Transmission of contaminated disease itself is thought to be low.
It widely thought that Xanthomonas campestris pv. musacearum bacteria is transmitted to airborne vectors through exposed male flowers (see plant reproductive morphology). Xanthomonas campestris pv. musacearum bacteria has been isolated from the ooze and nectar excreted from openings of fallen male flowers.Insects, namely stingless bees (Apidae), fruit flies (Drosophilidae) and grass flies (Chloropidae), transmit the disease from banana to banana after being drawn to the infected nectar. If the disease has been transmitted by insects the symptoms tend to first appear on the male buds of the banana plant.
The knife (panga) is used almost universally in African agriculture. Use of contaminated knives was a common method for disease spread when the disease first originated but increased knowledge of BXW transmission has led to increased numbers knives being disinfected after use. Herbicides are now advised as a more economical and effective way of destroying infected banana crop.
Infected plant material
BXW infects all parts of the plant. Disease spread has been primarily linked with the transport of plants shoots for replanting. Other parts of the plant such as the male buds (used in banana beer production) and mulch (banana waste material) can also expose novel regions to the disease.
No. Cultivated bananas are not yet available however the National Banana Research Program is currently conducting research into the development of bananas with such traits. So the best way to prevent BXW is by following recommended practices such as removing the male buds, removing infected plants, flaming prunning tools and others. You can read more about his on other pages on this website
No! M9 is a hybrid generated by cross pollination of two parental lines with useful traits.
The simplest way to define a hybrid is to take an example. Let us say a plant breeder in the Banana program observes a particularly good habit in a plant, but with small bunch size, and in another plant of the same type he sees big bunches but poor resistance to a disease such as the Black Sigatooka. The best plant of each type is then taken and self-pollinated (in isolation) each year and, each year, the seed is re-sown. Eventually, every time the seed is sown the same identical plants will appear. When they do, this is known as a 'pure line'.
If the banana breeder now takes the pure line of each of the two plants he originally selected and cross pollinates the two by hand the result is known as an F1 hybrid. Plants are grown from seed produced and the result of this cross pollination should have a disease resistance and good good bunch sizes.
This is the simplest form of hybridisation; there are complications, of course. A completely pure line can sometimes take seven or eight years to achieve. Sometimes, a pure line is made up of several previous crossings to begin to build in desirable features and grown on until it is true before use in hybridisation.
So the M9 is a hybrid banana which is resistant to the Black sigatooka and also produces bunches up to 71Kg.
Control of BXW is based upon a variety of methods to help prevent the spread of the disease. Vigilance and the quick removal of infected plants remain critical to minimising spread of the disease.
Infected plants can be removed using herbicides or more commonly by cutting the plant into small fragments and decomposing. The risk of infection can be lowered by removal of the male bud ('debudding') but many farmers believe this is essential to the quality of the banana fruit. The risk of infection decreases if the plants are not covered with topsoil. However the risk of disease should be balanced against the resulting decrease in yield of the banana plantain. A major part of disease control is the disinfecting of the tools used.
Much of the work in controlling BXW has been done through educational campaigns raising awareness of the disease to the banana farmers. For example: in Uganda and Tanzania where the government has actively worked alongside farmers to help limit spread of the disease, over 90% control of BXW has been reported. Moreover much of the information taught to the farmers can be used in the control of other banana infecting diseases.
No banana cultivars in Central and Eastern Africa have shown any resistance to BXW despite some varieties, such as those in the 'Pisang Awak' region, showing increased susceptibility.
However, Scientists have recently transferred two genes from sweet green pepper to bananas in order to confer resistance to BXW. This is a promising step forward in circumventing the time consuming and expensive practices of disease management such as 'debudding'.
Pflp and Hrap genes encoding the proteins plant ferredoxin-like amphipathic protein (pflp) and hypersensitive response-assisting protein (hrap) were isolated from sweet pepper and introduced to the genome of East African bananas using genetic engineering. The two proteins induced a hypersensitive response and systemic acquired resistance within the banana plant after being exposed to the bacterial pathogen. It was reported that over half of the transgenic bananas were resistant to BXW.
No. There are no known GMO bananas rleleased or commercialized in Uganda yet. What is available are the local bananas and the hybrids.
Tissue cultured banana plants are clean, disease free planting material that offer a more rapid method of multiplication of quality plants which are uniform in growth habits and such plants are the preferred method for large scale banana cultivation. Kawanda has a tissue culture laboratory for the production of such plants and there are a few private laboratories in Kampala that also produce such plants.
Ans. It was first reported in Ethiopia in 1960s. How it got into Uganda in 2001 is not clear, but what is important is that it is controllable so let us control it.
The vast majority of the bananas currently grown and consumed were not conventionally bred but are selections made over probably thousands of years from naturally occurring hybrids. Cultivated bananas are very nearly sterile and as a consequence are not propagated from seed but rather through vegetative propagation, primarily suckers as well as more recently micropropagated or tissue cultured bananas. These factors, very old selections, near sterility and vegetative propagation, mean that these bananas have not been genetically improved either for resistance or improved quality and are becoming increasing in affected by serious pests and diseases.
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