Musa

For a detailed discussion of bananas see http://www.hort.purdue.edu/newcrop/morton/banana

Wild Musa species

The genus Musa was traditionally classified into five sections (Ingentimusa, Australimusa, Callimusa, Musa and Rhodochlamys) but these have recently (2002) been reduced to three. Previously, the 2n = 20 chromosome species were separated into the sections Australimusa and Callimusa and the 2n = 22 chromosome species were separated into the sections Musa and Rhodochlamys. Recently, studies by Carol Wong and colleagues in Singapore have revealed that genetic differences between each section in the same chromosome group are smaller than those within each section. This means that the traditional separation of the sections can no longer be substantiated. Wong's studies do, however, maintain the separation between the 20 and 22 chromosome species. At present the 14 chromosome Ingentimusa section remains distinct.

Reference: Wong, S., Kiew, R., Argent, G., Set, O., Lee, S. K., and Gan, Y. Y., "Assessment of the Validity of the Sections in Musa (Musaceae) using ALFP." Annals of Botany 90 (2) : 231 - 238 (2002).

Ingentimusa section - from Papua New Guinea

Musa ingens

Callimusa section (incorporating Australimusa)

M. alinsanaya

M. beccarii [see note]

M. boman

M. borneënsis

M. bukensis

M. campestris

M. coccinea [see note]

M. exotica [see note]

M. fitzalanii [extinct]

M. flavida

M. gracilis

M. hirta [see note]

M. insularimontana [see note]

M. jackeyi

M. johnsii

M. lawitiensis

M. lolodensis

M. maclayi

M. monticola

M. muluensis

M. paracoccinea

M. peekelii

M. pigmaea [see note]

M. salaccensis

M. splendida [see note]

M. suratii [see note]

M. textilis (see also Abaca)

M. tuberculata

M. violascens

Musa section (incorporating Rhodochlamys)

M. acuminata

M. angcorensis [see note]

M. aurantiaca

M. balbisiana

M. banksii [see note]

M. basjoo

M. cheesmanii

M. flaviflora [see note]

M. griersonii

M. itinerans

M. laterita

M. mannii

M. nagensium

M. ochracea

M. ornata [see note]

M. rubra

M. sanguinea

M. schizocarpa

M. siamea [see note]

M. sikkimensis

M. thomsonii [see note]

M. velutina [see note]

M. sp. "Burmese Blue" [see note]

M. sp. "VN1-054"[see note]

Notes:

Musa angcorensis Gagnep. is poorly known and may not be a good species. It was placed very tentatively in section Callimusa but, if it exists at all, it is more likely to be section Musa.

Musa banksii F. Muell. is generally considered to be a distinct species rather than a form of M. acuminata.

Musa beccarii Simmonds is reported as having a chromosome number of x (= 1n) = 9 and 10, the latter due to multivalent formation during meiosis. Although genetically it nestles comfortably within section Callimusa the chromosome number needs clarification.

Musa coccinea Andrews has been confirmed as the correct name for the plant often called Musa uranoscopos Lour. in the literature.

Musa exotica Valmayor is newly described from Vietnam where it is known as Chuoi Rung Hoa Do. It has the correct chromosome number for section Callimusa.

Musa flaviflora Simmonds (one of the "parents" of M. ornata) should perhaps be treated as a sub-species of Musa acuminata Colla.

Musa hirta Becc. is a good species although poorly known and its affinities with M. beccarii suggest it belongs with that species in section Callimusa.

Musa insularimontana Hayata endemic to a single island off Taiwan is poorly known. It is close to M. textilis and is perhaps vulnerable to reduction.

Musa ornata Roxb. seems to be a "secondary species", a relic of a hybrid swarm between M. flaviflora and M. velutina.

Musa pigmaea Hotta (nomen nudum as yet) is a good species although enigmatic. Its reported affinity with M. beccarii suggests it belongs with that species in section Callimusa.

Musa siamea (comb. nov) is placed here somewhat prematurely but based on recent genetic evidence is likely to be elevated from M. acuminata subsp. siamea.

Musa splendida A. Chev. is poorly known and may not be a good species. A plant known as Chuoi gai, a name given by Chevalier for M. splendida, seems identical with M. paracoccinea but differs from Chevalier's description of M. splendida.

Musa thomsonii Noltie is a good species although very poorly known. However, seed has just become available commercially.

Musa velutina Wendl. & Drude may be the same as Musa dasycarpa Kurz in which case the latter would have priority.

Musa sp. "Burmese Blue" is placed here deliberately provocatively. It has been reported as being M.acuminata and M. balbisiana but seems different from both.

Musa sp. "VN1-054" is placed here rather speculatively. Known in Vietnam as Chuoi Rung Hoa Soan it has been confused with Musa itinerans although differing in its remarkable imbricate male bud. That it is a hitherto unknown species is reported here for the first time.

Edible bananas

A number of distinct groups of edible bananas have been developed from species of Musa. By far the largest and now the most widely distributed group is derived from Musa acuminata (mainly) and Musa balbisiana either alone or in various hybrid combinations. The next but much smaller group is derived from members of section Callimusa (previously classified as Australimusa) and is restricted in importance to Polynesia. Of even more restricted importance are small groups of hybrids in Papua New Guinea; a section Musa group to which Musa schizocarpa has also contributed and a group of section Musa x section Callimusa (previously classified as Australimusa) hybrids.

From the time of Linnaeus until the 1940's different types of edible bananas and plantains were given Linnaean binomial names, such as Musa cavendishii as if they were species. In fact, edible bananas have an exremely complicated origin involving hybridisation, mutation and finally selection by humans. The giving of species names to what are actually very complex hybrids led to endless confusion in banana botany. In the 1940's and 1950's it became clear that the cultivated bananas and plantains could not usefully be assigned Linnean binomials. An alternate genome-based system for the nomenclature of the section Musa bananas was devised.

As mentioned above, the main group of edible bananas are derived from Musa acuminata and Musa balbisiana. As an example of the application of the genome based nomenclature system, the plant known by the "species" name Musa cavendishii became Musa (AAA group) 'Dwarf Cavendish'. The "new" name shows clearly that 'Dwarf Cavendish' is a triploid, with three sets of chromosomes, all derived from Musa acuminata designated by the letter "A". When Musa balbisiana is involved the letter "B" is used to denote its genome. Thus the variety 'Rajapuri' is correctly written as Musa (AAB group) 'Rajapuri'. 'Rajapuri is also a triploid with two sets of chromosomes from Musa acuminata and one from Musa balbisiana. In the edible bananas genome combinations such as AA, BB, ABB, BBB and even AAAB can be found.

No such nomenclature system has been developed for the next group of edible bananas derived from section Callimusa (previously Australimusa). However, this group is known generally as the "Fe'i" or "Fehi" bananas and there are numerous cultivars of this group in the South Pacific region. They are very distinctive plants with upright fruit bunches (edible banana bunches normally hang down) and feature in three of Paul Gauguin's paintings. The flesh must be cooked before eating, is bright orange and can colour the ingestor's urine. The Fe'i bananas are no longer very important for food, although some have ritual significance. It is probable that the Fe'i bananas derive mainly from Musa maclayi although their origins are not as well understood as the section Musa bananas. Varieties can be formally named as in this example, Musa (Fe'i group) 'Utafun'.

External links and references

• Suzanne Sharrock, Diversity in the genus Musa, focus on Australimusa http://www.inibap.org/publications/annualreport/focus100.pdf
• Sturtevant's Edible Plants of the World, J. B. Lyon Co., Albany, 1919
• David Constantine, The Genus Musa, http://www.users.globalnet.co.uk/~drc/genusmusa.htm#start