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View Full Version : How did we get dwarf varieties?


sputinc7
08-27-2016, 05:55 PM
I'm sure this has been covered somewhere, but quite frankly, I am tired of looking. It's probably right under my nose, but I must be searching in the wrong places or something. Anyway, how did they come about? i.e. If a Highgate is still a Gros Michel How come it's shorter without the fruit being different?

Gabe15
08-28-2016, 11:11 AM
Dwarfism is one of the most common mutations to occur, and it can more or less happen randomly. Over the thousands of years bananas have been cultivated, many mutations or "sports" have occurred, and if it was something that was interesting to the grower, it would be maintained.

Imagine you have a large plant that routinely fruits at 15ft high, and one day you notice a sucker which seems stockier and is not gaining as much height with each new leaf. So you keep an eye on it throughout it's growth and one day it fruits, but it is only 5ft high. Perhaps another sucker comes off that sucker and behaves the same way, so you separate it off and replant it elsewhere, and it keeps staying stocky and fruiting short, now you have selected a dwarf variant.

This same process for all of the mutant variations that have occurred within the different subgroups of edible bananas that give us a spectrum of closely related, but different cultivars. Not all mutations are equal, and most of the time they are not desirable, and so they are not maintained.

In the case of 'Highgate' specifically, the plants are much shorter, but so is the fruit, so it is not commonly grown commercially. 'Cocos' however, which is a different dwarf Gros Michel cultivar, has much larger fruit and comparable to the more standard tall Gros Michel cultivars. Any number of combinations of traits may be produced when mutations occur,

This same principle of mutation and selection can also be observed with tissue cultured plants, where because you are producing so many plants at a greatly accelerated propagation rate the mutation rate is also very high (and perhaps there is some aspects of the tissue culture techniques which directly encourage mutations in some cases), and so plants coming from tissue culture must be careful managed and observed to catch what are called "off-types" which are undesirable mutations. Selecting tissue culture variants can also be used as a form of breeding if you find a desirable mutation.

One other method of specifically producing dwarfs is by deliberately creating mutations by exposing young tissue cultured plants to ionizing radiation which can cause DNA damage, and thus mutations. This technique is called radiation induction. A range of mutations will occur, and some may be dwarfism. The only widespread cultivar to have been produced in this way is the 'Super Dwarf Cavendish', which although very dwarf, has a number of other issues which make it somewhat undesirable for fruit production.

sputinc7
08-28-2016, 12:58 PM
Thank you mucho Gabe... I appreciate your thoroughness. I kinda found hints here about it being accidental but wasn't sure how that came about.