Going bananas for plant tissue culture
Did you know that the banana plant is the largest flowering herb?
That’s right, bananas do not come from trees. The plant has no hard woody parts and is therefore not a tree. Rather it is a herbaceous plant. Additionally, the banana plant’s fruit is botanically an elongated berry. And there is yet another distinction to be made. The fruit of the banana plants are either dessert bananas or plantains. The dessert banana is the fruit we eat raw and add to our smoothies. While the plantain is a more starchy and less sweet fruit that is green, yellow, or black. Plantains are cooked and usually not eaten raw.
The growing demand for bananas
This eccentric fruit is still growing in popularity. Global banana consumption reached 88,374 kt in 2018 according to the Food and Agriculture Organization (FAO) of the United Nations. That works out to be approximately 85.9 kg of bananas per year for each person globally in 2018. And the global demand is constantly increasing. From 2008 – 2018 the global consumption of bananas increased by over 13 % and does not show signs of slowing down. However, this industry is under threat. A 25 billion USD variety known as the ‘Cavendish’ banana may go extinct due to a virus known as the Tropical Race 4, or due to Panama disease, a fungus that's now ravaging banana farms across the globe.
Extinction is the reason banana-sweets don’t taste like ‘real’ bananas
Before the Cavendish banana became a global superstar, a different banana variety held that title. In the mid-19th century, a banana known as the ‘Gros Michel’ was the commercial variety of choice. Mainly due to its thick skin making it easy to transport. However, this variety became commercially extinct in the 1960s after the crop was severely plagued with Panama disease in the 1950s. The Cavendish was resistant to this disease, and as a result, took over as the new commercial banana of choice. The Gros Michel variety contains more of the compounds that current synthetic banana flavorings have. This is why synthetic bananas do not taste like ‘real’ bananas, which are associated with the Cavendish banana.
Plant tissue culture fighting against disease
With the threat of another major commercial banana variety going extinct, what can be done? The Gros Michel banana is a learning curve for the banana industry. The variety went commercially extinct rather quickly as the ‘gene bank’ was not curated. In other words, there was little genetic information available about this banana in research laboratories. Now with plant tissue culture (PTC) it is possible to preserve genetic material. The ability of PTC to rapidly produce genetically identical explants that are completely disease free has a significant impact on the security of the genetics.
Additionally, PTC can multiply varieties that are resistant to diseases. For example, researchers are able to create resistant Cavendish varieties via genetic modification or cross breeding. A genetically modified version (GMO) of a Tropical Race 4-resistant Cavendish already exists.
Why are banana farmers switching to PTC over conventional methods?
Commercial bananas are only propagated by vegetative means. This is because most bananas are sterile and that is why they don’t have seeds. The banana has a reduced underground stem, called the rhizome, which yields several buds. Each of these buds sprouts and forms its own new stem and a new bulbous rhizome. Conventional propagation techniques use these daughter plants which they call ‘suckers’. However, these suckers can often be infected with Panama disease as the disease-causing fungal microspores are present in the soil.
Plant tissue culture and commercial banana production are a match made in heaven. Micropropagation was the first biotechnology used in the commercial banana industry. Recent research has stated that the net returns were 11.1 % higher for PTC compared to conventional sucker propagation. However, this is not the best result cited. Other studies have found even greater success rate due to better implementation of PTC methods as well as farming practices.
Commercial in vitro micropropagation of bananas focuses on embryo and meristem cultures. Of these two methods, meristem culture from the shoot tip is most successful. You can read our article ‘Meristem tissue culture’ for further information on meristem culture.
The golden glow of PTC bananas
A recent study compared the profits of conventional and PTC banana farmers. The results are astonishing. PTC methods made high quality banana plants more readily available. These plants had better market related qualities and showed better disease resistance. Thereby, improving production in some places by 155.5%. And the good news doesn’t end there. Incorporating PTC methods increased the value of production by 25%. Allowing the PTC banana farmers to sell their goods at a higher price compared to their traditional banana farmer counterparts. Resulting in the PTC farmers increasing their average profits by 591% compared to conventional farmers.x
By Christos Tripodis | 3-January-2022
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