ryan

Could someone explain the banana groups like AAA, AB, and what they mean. I'm really lost here.

Richard

A long time ago in a place far away ... there were species bananas (Musa). These plants produce seeded fruits -- and by seeds I mean pea-sized seeds hard as a rock. You'll find many listed in the Bananas Wiki. Each of the seeded species has a certain genotype: A, B, T, S -- briefly charted here: INFO Genetic Names - Bananas Wiki. Over the millenia these interbred and in human times have been purposely cross-bred to produce hybrids: almost all of which are seedless bananas, and many of which are edible. So for example, an AAB was created by selected crossing of Musa acuminata x Musa acuminata x Musa balbisiana.

Banana "group" names refer to entire sets of bananas with the same geneology and similar phenotype. Musa researchers formally call these "subgroup taxons". Some examples are: Pome, Mysore, Cavendish, Celat, Iholena, Maoli, Pisang Wawak, Pitogo. Just to make it more interesting, there are also individual bananas with the same name as the group they belong to.

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ryan

then how does the 5 subgenera (eumusa etc ,) come into play?

thanks for the help thus far. really useful info!

btw, should it be 'phenology', or rather, 'phenotype'?

Dean W.

Well said, Richard! I'm still a newbie so it helps.

Dean

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Richard

Good point!

Since I'm relatively new to bananas myself, I will leave this for inkcube , Gabe15 , pitangadiego , and several other banana gurus at this site to answer.

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Gabe15

The following are excerpts from a paper I wrote on bananas for botany class.


SUGENERA/SECTIONS:
The genus Musa, native from Northern India to Papua New Guinea, is divided into five subgenera which are currently separated genetically, morphologically and geographically. The subgenera Eumusa and Rhodochlamys both have chromosome counts of n=11, but are separated by distinct morphology, growth habit and native range. Eumusa may be diploid, triploid or tetraploid (2n=22, 3n=33, 4n=44, respectively). Synthesized ploidly levels beyond tetraploid result in weak, non vigorous plants which often die young or remain virtual permanent seedlings. The subgenera Callimusa and Australimusa both have the chromosome count of 2n=20, but are separated by distinct seed morphologies and geographic range (though M. textilis is now widespread). Musa ingens, the sole member of the Ingentimusa subgenera is native to the highland mountains of Papua New Guinea and has a distinct chromosome count of 2n=14. One known aberration to these subgenera is Musa beccarii of the Callimusa (based on general appearence, not genetics) which has the anomalous chromosome count of 2n=18 and a unique seed form not consistent with other Callimusa.

adapted from- Sharrock, Suzanne. Uses of Musa. INIBAP. Montpellier: INIBAP, 1997. 42-44.


EDIBLE BANANA GENETIC GROUPS:
Most edible bananas belong to the subgenera of Musa called Eumusa. Two species, Musa acuminata and M. balbisiana, are the primary progenitors of the edible bananas, though M. schizocarpa and M. textilis (the latter being of subgenera Australimusa) do in fact contribute genetically to a small number of cultivars. Through a few chance mutations and multiple crosses and backcrosses, bananas came to be something that humans could easily eat, much different from the seedy wild congeners. Since edible bananas are so highly evolved from their wild cousins, giving them classic Linnean binomials does not make sense. Taxonomists struggled for years trying to classify the edible bananas, but it wasn’t until the work of Simmonds and Shepherd in the 1950’s that a system was devised to logically classify the edible bananas. The system, which is still the standard today, is based on the scoring of 15 phenotypic characteristics on a scale from 1-5, 1 being a trait which is very M. acuminata like and 5 being a trait which is very M. balbisiana like. The summation of the scores judged for each variety segregates cultivars into genome groups based on ploidy level and relative contributions of each parent species. For example, a diploid cultivar derived completely from M. acuminata will be given the designation (AA), while a triploid would receive (AAA). If M. balbisiana was involved in its evolution at some point, traits would show in the plant and a placement of (AB), (AAB), (ABB) would be given depending on ploidy level and relative genetic composition. Cultivars are then properly written as (for example) Musa (AAA) ‘Williams’ or Musa (AAB) ‘Dwarf Apple’. This system can be used in the field to quickly identify cultivars to the genome level, while DNA test may confirm them if needed later on.

Simmonds, N.W. The Evolution of the Bananas. London: Longmans, 1962.

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ryan

thanks gabe,

that was really clear as to how the edible banana genetic groups are derived.

this system is indeed useful in attaching the group to the cultivar and thus knowing whether it is a dessert or cooking banana, due to either parent's influence. This is as far as a general banana enthusiast would go with such information.

on another note, the tetraploidy aspect seems particularly interesting, eternal seedlings? pictures pictures! what do these look like?

then again, how do we explain hybrids when the bananas we work with are seedless? there's this school of thought whereby some seedles ones do have 1 or 2 seeds oncein a while and those are sown.... what do u think?

Gabe15

The plants beyond tetraploid (tetraploids are fine, just like pentaploids, hexaploids...those don't work) are the results of dead ends in breeding programs, they are obviously not a good choice plant to breed with so they don't make it anywhere.

As for seeds in edible bananas, this is not as weird as it sounds. The reasons for sterility are complex and vary between individual varieties. The more "advanced" cultivars have been chosen to be completely sterile, this means they cannot receive or produce pollen essentially. However, before there were advanced cultivars, they could all form seeds and there are still many of these around. The reason you don't see seeds in Cavendish bananas is because they cannot be fertilized and even if they could there is no pollen being produced anywhere. Some edible varieties can receive pollen, but if there is not a pollen source they will not form seeds, but sometimes wild plants or other varieties that do produce fertile pollen could be nearby and so you may find a few seeds in those varieties capable of forming them.

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jpfloors

Thanks for all of the great info Gabe!

dsws

Ploidy is increased by crossing, but is it ever decreased?

Gabe15

When breeding with anything parthenocarpic, the resulting progeny can vary in their ploidy. So a 2n x 4n will produce a number of 3n as expected, but can also produce 2n, 4n, 5n, 6n, or 7n progeny. Beyond 4n however, the plants are typically weak and generally non-viable.

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Growing bananas in Colorado, Washington, Hawaii since 2004. Commercial banana farmer, 200+ varieties.