Team:Hong Kong-CUHK/Description
Description
How Much Do You Know about Banana?
Banana is one of the most favorable tropical food due to its high nutritional value [1]. It has high potassium content which is important for maintaining our body fluid balance, regulating muscle contractions and maintaining a healthy nerve function. Thus, bananas is generally very good food for people to eat.
Moreover, banana is a kind of high-carbohydrates fruits. It is a very important crop for people in Africa. It contributes to half of the household diet in one-third of the Rwanda families [2]. Without bananas, the lives of people in Africa could be affected.
Banana is not only important to people’s diet but the production of banana also creates high economic value. In 2016, the retail value of banana trading is around USD20-25 billion [3]. Therefore, bananas are important because it provides people with energy and nutrient, and is also a crop for farmers to make a living.
Banana Xanthomonas Wilt
Banana disease Banana Xathomononas Wilt (BXW) is a bacterial infection caused by Xanthomonas campestris pv. musacearum (Xcm) and is reported in 2002 [4]. Xcm can be transmitted by soil [6], air [7], farming tools [8] and infected plant materials [9]. BXW can result in severe yield loss as high as 100% if control is delayed. In Tanzania and Rwanda, 35 % drop in sales and doubling of banana price due to BXW were reported. In Uganda, production in 2014 was 50% less than that in 2002 while the area of banana farmland was declined by 39%.
This disease may spread very fast and may eventually lead to a decrease in the supply of bananas. This may hinder the living of farmers at the same time. We believe that this precious fruit should be protected so that people all over the globe can get them easily from the markets and sustain the living of African by feeding themselves enough bananas.
Pathological Control of BXW
Banana Xanthomonas Wilt is spreading quickly from the hot eastern DR Congo to the Congo Basin. Within the affected countries, the disease has spreaded to new zones at rates depending on the agroecological conditions and the characteristics of the production systems. Lower altitude areas (<1500 m) were reported to have a high spreading rate. Reports also pointed out that BXW had a long incubation period up to 24 months and had a latent infection phase. Over the past 15 years, various research and extension efforts have been put in place to manage and contain the disease. No disease quarantines have been set up in the region to isolate the disease, low success rates are anticipated due to lack of efficient detection tools at border points.
How to Detect BXW
Direct observation
Currently, farmers can only notice the late phase BXW infection through direct observation of the banana trees. Typical symptoms of BXW infection are: banana leaves turn yellow, male bud drying, uneven ripening and the presence of yellow bacterial ooze in the vascular tissue (figure 3). However, these symptoms are only visible when the bananas are seriously infected, and it takes at least two months for the arise of symptoms.
DNA amplification
In a laboratory setting, BXW disease can be detected by DNA amplification by polymerase chain reaction (PCR) or loop-mediated isothermal amplification (LAMP). DNA sample extracted from the banana leaf is mixed with a specific set of primers to amplify the GspD gene of the bacterial Xcm genome. This method is fast and sensitive but it is not commercially available in the market for mass screening, as the amplification technique may show false-negative results when uninfected regions are sampled. Also, this method is not feasible for African farmers since it requires expensive laboratory apparatus and skilled workers.
Flow device
The latest detection strategy is a lateral flow device reported in a recent paper [5]. This lateral flow device detects target antigen from the homogenized leaf extract by the specific antibody coated on the test strip. This device is simple and suitable for field detection. However, it also has a chance to show false-negative results and it is still not available in the market. As a result, African farmers have no alternative ways other than naked-eye observations.
Thus, to tackle the problem of BXW, an early disease diagnosis method that can be used in a lab free condition is essential for the farmers to identify infected plants and uproot them at an early stage to minimize loss. The first step is to develop an accurate microbiological system that can detect the infection at an early stage. At this time point, we have already designed and modeled a molecular detection pathway and the device. In the future, we hope to find ways to cure the disease and to minimize loss.
References
[1] Food Composition Databases Show Foods -- Bananas, raw. (n.d.). Retrieved from https://ndb.nal.usda.gov/ndb/foods/show/09040?fgcd=&manu=&format=Full&count=&max=25&offset=&sort=default&order=asc&qlookup=09040&ds=&qt=&qp=&qa=&qn=&q=&ing=
[2] Development of ICT Innovation Expected to Help in Fight Against Banana Disease in Rwanda. (2019, April 1). Retrieved from http://www.ipsnews.net/2018/09/development-ict-innovation-expected-help-fight-banana-disease-rwanda/
[3] Why bananas matter. (n.d.). Retrieved from http://www.bananalink.org.uk/why-bananas-matter
[4] Development of ICT Innovation Expected to Help in Fight Against Banana Disease in Rwanda. (n.d.). Retrieved from http://www.ipsnews.net/2018/09/development-ict-innovation-expected-help-fight-banana-disease-rwanda/
[5] Hodgetts, J., Karamura, G., Johnson, G., Hall, J., Perkins, K., Beed, F., ... & Smith, J. (2015). Development of a lateral flow device for in‐field detection and evaluation of PCR‐based diagnostic methods for Xanthomonas campestris pv. musacearum, the causal agent of banana xanthomonas wilt. Plant pathology, 64(3), 559-567.
[6] Tripathi, L., Mwangi, M., Abele, S., Aritua, V., Tushemereirwe, W. K., & Bandyopadhyay, R. (2009). Xanthomonas wilt: a threat to banana production in East and Central Africa. Plant Disease, 93(5), 440-451.
[7] Smith, J. J., Jones, D. R., Karamura, E., Blomme, G., & Turyagyenda, F. L. (2008). An analysis of the risk from Xanthomonas campestris pv. musacearum to banana cultivation in Eastern, Central and Southern Africa. Bioversity International, Montpellier, France. ISBN, 978-2.
[8] Blomme, G., Turyagyenda, L. F., Mukasa, H., & Eden-Green, S. (2008). The effectiveness of different herbicides in the destruction of Banana xanthomonas wilt infected plants. African Crop Science Journal, 16(1).
[9] Smith, J. J., Jones, D. R., Karamura, E., Blomme, G., & Turyagyenda, F. L. (2008). An analysis of the risk from Xanthomonas campestris pv. musacearum to banana cultivation in Eastern, Central and Southern Africa. Bioversity International, Montpellier, France. ISBN, 978-2.