www.BioTopics.co.uk
Site author Richard Steane
The BioTopics website gives access to interactive resource material, developed to support the learning and teaching of Biology at a variety of levels.

Bananas, asexual and sexual reproduction



Most sweet bananas grown today are from a single variety - " Cavendish" - produced as a result of asexual reproduction, not from seeds.

In order to meet the world demand for this fruit, banana plants are grown in several tropical countries, many of which are islands. In Africa, different species (some called plantains) are used, and prepared to be eaten in different ways.

In these places, they are the main crops (an example of monoculture).

The crop may be damaged by weather conditions - tornadoes are a constant menace - or as a result of diseases - especially fungus diseases.
Just like the Irish potato famine, there have been several instances of banana crop failure due to fungus disease. One fungus disease ("Panama disease" caused by Fusarium oxysporum) has been through several stages, widespread crop damage being prevented each time by use of fungicides and changing banana varieties grown. Another disease ("Black Sigatoka" caused by Mycosphaerella fijiensis) is a possible threat in the future.

In fact the way that bananas are propagated from shoots at the base of the tree may spread fungal infections as fungal spores may be in the small amounts of soil transferred at the same time. This soil transfer may be avoided if shoots are used to produce a bulk of clean new plants by micropropagation, which also relies on asexual reproduction.

Would these plants produced by micropropagation be resistant to the fungal diseases?

> No - they are genetically identical to the parent plant, unless resistance genes are obtained from another variety or species - a good candidate for genetic manipulation.

It is said that the bananas available today (resistant to the previous fungal strains) are not as tasty as the varieties of banana (especially Gros Michel) which used to be grown before these disease outbreaks (up to the 1950s), but there are also fears that new fungal strains will evolve.

Web references

http://www.popsci.com/scitech/article/2008-06/can-fruit-be-saved Can This Fruit Be Saved?
The banana as we know it is on a crash course toward extinction. For scientists, the battle to resuscitate the world's favorite fruit has begun—a race against time that just may be too late to win

http://www.apsnet.org/education/feature/banana/Top.html
The most important disease of a most important fruit

http://www.freshplaza.com/news_detail.asp?id=9463
Australia: Soil fungus hitting NT banana trade

http://www.newscientist.com/article/mg19025513.700-a-future-with-no-bananas.html
A future with no bananas?

http://www.newscientist.com/article/mg17723784.800-going-bananas.html?full=true
Going bananas





www.BioTopics.co.ukHome Contents Contact via form Contact via email Howlers Books WWWlinks Terms of use Privacy