It's an herb not a tree
Banana fruits are one of the top ten fruit crops in the world. The banana is actually a giant berry and the banana plant is the world's largest perennial humongous herb that is grown throughout the year. In other words, the banana plant is not a tree. The banana plant can grow up to 25 feet and the leaves can extend to 9 feet. It's difficult to pinpoint the origin of bananas but it's strongly believed to have originated in Malaysia.
When we think of the banana it is almost invariably the yellow banana. The yellow banana is a mutant strain of plantain belonging to the genus plantago. There are in excess of 300 banana varieties. The predominantly traded variety of the banana is the Cavendish which can be found mostly in Philippines.
As a thumb rule, bananas can be cultivated on either side of the equator where the climate is hot and humid like for instance in Central America, Caribbean, and S.E.Asia.
Nutritional benefits of the banana
Bananas are rich in potassium, manganese, vitamins and fiber but low in fat. It is sodium free, cholesterol free and a great source for Vitamin B-6 (helps in hemoglobin production) and vitamin C. So in a way it meets the dietary requirements especially of the developing world.
Children taking a banana a day have less chance of getting asthma. For adults the risk of getting colorectal and kidney cancer is reduced and so is the risk of leukemia if bananas are eaten regularly.
Bananas are useful as a diet supplement for weight loss programs. The reason is, bananas contain resistant starch (which increases fat metabolism) and prebiotic fiber that precludes unhealthy weight gain from occurring.
Diseases associated with bananas
The banana plant is susceptible to disease, and if disease sets in, it is difficult to control the spread of disease. It is here that biotechnology plays a great role in not only ensuring that the banana plants do not contract disease, but in also ensuring the sustenance of the banana plant in the future.
The two ascomycetous fungi Mycosphaerella fijiensis (responsible for black leaf streak disease) and Mycosphaerella musicola cause the Sigatoka disease in banana plants. The Sigatoka is a leaf spot disease that could reduce yields by as much as half. It could also cause premature ripening of the fruits after plucking. In the normal course, to escape from this disease, it means the farmer would have to adopt costly chemical control methods which would be beyond the means for a marginal farmer as costs would go up by about 15%. Another problem is fungicide resistance which would make controlling this disease even more difficult.
In order to genetically breed banana plants that is resistant to Sigatoka disease, crosses are made between commercial triploids and improved diploids. Natural resistance to this disease can be found in diploid cultivars such as Paka(AA),Pisang lilin (AA), and in wild M u s a (Musa means one of three genera in the family Musaceae that includes bananas )species like M. a c u m i n a ta ssp., b u r m a n n i c a, ssp., m a l a c c e n s i s a n d ssp. The first step is to obtain improved (AA) diploids. These are crossed with triploids to get (AAAB) tetraploids which are cells that have four sets of chromosomes. By combining genetically different diploids it is possible to make different hybrid banana plants that are resistant to disease.
To get resistance from yellow Sigatoka and nematode simultaneously, a possible crossing would be between Jari Buaya diploid (with nematode resistance) and Microcarpa
Root-lesion causing plant nematode (or roundworm) Pratylenchus coffeae and root-knot nematode Meloidogyne incognita is a problem with banana plants grown in Asia. Root lesion nematodes cause sparse root growth and also lack of feeder roots. Therefore as bananas are top heavy plants, root nematodes can cause havoc. Besides it can reduce the fruit bunch weight and lengthens the time required for banana fruits to form. The biotech solution to this problem is to use the bio-fungicide Trichoderma viride. The flower petal extracts of Tagetus erecta (commonly known as Mexican Marigold) can also be used to combat banana plant nematodes.
DiTera is an interesting new proprietary biological nematocide made from the microorganism Myrothecium spp that can be used on banana crops to counter nematodes from causing disease.
Another method to counter nematodes is to use resistant varieties like banana hybrid FHIA-25
The Odoiporus longicollis Oliver commonly known as the banana stem weevil is a dangerous pest that causes holes in the banana plant stem and lead to rotting. The result is, plant growth is retarded and the plant becomes susceptible to influx of wind, mainly because of a weakened stem due to larval tunneling. Some varieties of banana plants are more susceptible to stem weevil especially Nendran (a type of Indian banana).
Beauveria bassiana swabbed on the stems can effectively kill the corm and stem weevil. However, biotech research in developing products to combat stem weevil attack has not produced much practical results. But research in developing plants resistant to stem weevil has been successful in producing varieties like Pisang Jari Buaya (AA), Pisang Lilin (AA), Elavazhai (BB) and Sapkal(ABB).
Cutting edge technologies for combating black sigatoka in banana plants
Farmacule and Demegen are outfits that have developed new technologies for combating black sigatoka. The novel expression technology of Antimicrobial peptides or AMP's developed by Farmacule enable disease control traits to be incorporated in banana plants and in combating microbial infection. This technology facilitates controlling protein expression implants. Demegen makes peptides when expressed in plants provide the plant with resistance to various diseases.
Panama disease in banana plants
Technically this disease is called Fusarium wilt that is caused by the fungus Fusarium oxysporum f.sp. cubense. This disease could lead to reduced yields and death of the banana plant. But the biggest problem is the soil remains infected and so the next crop could also face the same problem. The biotech solution to this problem is the development of resistant varieties like Williams, Paz, Valery and Giant Cavendish.
Another disease is anthracnose disease of banana. This can be controlled by spraying 25% percent leaf extract of Solanum tarvum.
Other biotech applications
The fruits that cannot be sold for one reason or the other can be converted to fruit pickles. The waste banana male bud can be converted to flower pickle. Both entail biotech methods.
Using enzymatic liquefaction process banana juice can be made from banana pulp.
The human papillomavirus could cause genital warts and plantar warts. Now bananas have been developed that contain this vaccine
Biotechnology in the context of bananas is important, as a majority of banana growers are small farmers (monoculture plantations) for whom banana crop constitutes a major source of income. So if disease hits the crop it hits the farmer very badly as well.
There are several shortcomings in the research focus on banana biotechnology. For example, there is as yet no popular solution to viral diseases like Banana Bunchy Top, and in Asia for the wilt disease caused by Triclomataceae fungus of Basidiomycetes. Similarly, products to counter stem weevil are only in the experimental stage.
But there are some plus points too. From a consumer perspective, The Rainforest Alliance approves banana farms that meet their certification standards in the use of agrochemicals, waste management processes and sustainable farming practices. So when you buy bananas cultivated in farms that bear the Rainforest Alliance seal of approval, you can be assured that they come from farms that do not use dangerous pesticides and would most likely be using biotech solutions.
At the research level, the development of the Musa germplasm Information system (MGIS) by INIBAP, France for conservation of Musa genetic resources is of great help to researchers. Similarly there are government sponsored banana germplasm banks in several countries to help ongoing research efforts.
In short, biotechnology aims to produce banana cultivars that give better yield with less of chemical inputs especially for farmers who depend on it for subsistence, and for the consumer it ensures a healthy fruit.
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