BANANA – Name, Taxonomy, Botany

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The edible bananas of the world belong to the Eumusa section of the genus Musa, except for the Fe‘i group, which belong to the Australimusa section. The Fe‘i bananas are characterized by erect bunches, pink-red to purple sap and deep yellow or orange colored fruit pulp. Banana and plantain (Musa spp., or Musa in this document) are giant perennial herbs which originated in Southeast Asia.

The cultivated banana is often listed in botanical references as Musa x paradisiaca (Musaceae), although it is actually a complex hybrid derived from two diploid Asian species, M. acuminata and M. balbisiana. Musa acuminata is a species native to the Malay Peninsula and adjacent regions and is thought to have given rise in total or in part to all edible banana varieties. Musa balbisiana is found from India eastwards to the tropical Pacific. This hybridisation probably occurred as Musa acuminata plants (2n genome = AA) were increasingly cultivated over the distributional range of Musa balbisiana (2n genome = BB). Although the Musa acuminata cultivars were sterile because of being seedless, they did produce fertile pollen.

Common cultivated bananas are sterile usually triploid (3n) with three sets of chromosomes triploid and they are products of ancient hybridization between diploid and tetraploid species. Musa species are grouped according to “ploidy,” the number of chromosome sets they contain, and the relative proportion of Musa acuminata (A) and Musa balbisiana (B) in their genome. Most familiar, seedless, cultivated varieties (cultivars) of banana are triploid hybrids (AAA, AAB, ABB). Diploids (AA, AB, BB) and tetraploids (AAAA, AAAB, AABB, ABBB) are much rarer; the latter essentially being experimental hybrids. Fruits of cultivated Musa species are typically sterile or have extremely low fertility. They produce fruit pulp without pollination and fruits lacking seed (i.e., they are parthenocarpic). Although sterility and parthenocarpy are important factors that contribute to the desirability of banana fruits, sterility has impeded progress in breeding programs. Through natural somatic (vegetative) mutation, hybridization, and selection over many thousands of years, considerable genetic variability has arisen within the cultivated bananas, giving rise to more than 1000 varieties worldwide.

Plantain and banana cultivars evolved by natural hybridization between the two species M. acuminata (contributing genome A) and M. balbisiana (contributing genome B). All plantains and almost all important bananas are triploid (2n = 3x = 33 chromosomes). Plantain and banana are monocotyledonous plants, belonging to the section Eumusa within the genus Musa of the family Musaceae in the order Scitamineae.There are five taxonomic sections in the genus Musa, two of which contain edible bananas. Therefore, banana and plantain (Musa sp) all belong to:

Kingdom: Class: Order: Family: Genus: Section: Species: Groups:

Plantae Monocotyledonae Scitamineae Musaceae Musa Eumusa M. acuminata (AA) M. balbisiana (BB) AAA dessert and highland beer and cooking bananas AAB plantains and dessert bananas ABB cooking bananas

Several criteria are used to distinguish the different types of plantain and banana further:

a) Form of consumption:	Plantain and cooking/beer banana are easily distinguished from dessert banana by their method of consumption. Plantain and cooking /beer banana require some form of processing, whereas dessert banana is eaten raw when ripe.
b) Inflorescence type:	All banana cultivars have the same type of inflorescence (or ‘bunch’).

Plantains have different types, and this can be used to subdivide and classify plantains.
Bananas have the complete Musa inflorescence: female flowers, neutral flowers (which do not develop into fruits, and fall off during bunch maturation), and a terminal male bud. Plantain is subdivided into:

1. French plantain (also called ‘Hembra’)
2. French Horn plantain
3. False Horn plantain (also called ‘Macho’, ‘Harton’)
4. Horn plantain

The subdivision depends upon:

1. completeness of inflorescence at maturity
2. presence of neutral flowers and male bud at maturity
3. number of hands
4. number and weight of fingers

(See Table 2 for details)

Table 2. Classification of Musa according to inflorescence type (See diagram below)

Group	Inflorescence	Neutral flowers	Male bud	Hands (no.)	Fingers (no)	Fingers (g)
Banana	Complete	Many	Yes	5-10	65-155	100-300
French plantain	Complete	Many	Yes	6-12	60-170	10-300
French Horn plantain	Incomplete	Many	No	7-8	30-85	200-300
False Horn plantain	Incomplete	Few	No	5-12	25-80	230-400
Horn plantain	Incomplete	None	No	1-5	1-50	250-610

French plantain: The inflorescence is complete at maturity. Hands consist of numerous rather small fingers, followed by the bunch axis covered with persistent neutral flowers. The terminal male bud is large and persistent.
False Horn plantain: The inflorescence is incomplete. Hands consist of large fingers followed by a few neutral flowers. At maturity, no male bud is present.
French Horn plantain: The inflorescence resembles the inflorescence of False Horn plantain, but French Horn has many more neutral flowers.
Horn plantain: The inflorescence is incomplete. There are few hands, consisting of a few large fingers. Neutral flowers and male bud are not present. A tail or protuberance terminates the bunch axis. Horn plantain resembles False Horn plantain, but has larger fingers and no neutral flowers

c) Height of pseudostem:	The height of the pseudostem, that is, the distance between the soil and the petioles of the highest leaves, is used for sub-grouping plantain cultivars into ‘giant’, ‘medium’, and ‘small’. Musa clones with short internodes are called ‘dwarf’ cultivars.
d) Genome composition:	Genotypes are classified by the genome composition, that is, the expression of M. acuminata and M. balbisiana characteristics (Dessert banana , some cooking and beer bananas are categorized as AAA, plantains as AAB, and cooking bananas as ABB.

Plant: Banana are species of the genus Musa are native to Southeast Asia but are now grown extensively in all tropical countries for their fruit, fiber, or foliage. As the banana plants are normally tall and fairly sturdy they are often mistaken for trees, but their main or upright stem is actually a pseudostem (literally “fake stem”). It is a large, perennial, monocotyledonous herb that arises from large, subterranean rhizomes (usually called “corms”), from which the plant is perpetuated by sprouts or suckers.For some species this pseudostem can reach a height of up to 2–8 m, with leaves of up to 3.5 m in length. Each pseudostem can produce a bunch of yellow, green or even red bananas before dying and being replaced by another pseudo-stem. In the tropics the stems are annual—that is, they die after perfecting the fruit, and new stems are developed from buds in the rootstock. These stems, or buds, are the common means of propagating and making new plantations, and the growth is so rapid that the fruit is usually ripe within ten months after the offsets are planted. When fully grown the stem attains a height of 3 to 12 m and is surmounted by a crown of large oval leaves up to 3 m long, with a strong fleshy foot stalk and midrib. The banana is the fast growing herbaceous plant consisting of one or more pseudo-stem (upright, trunk like structures) that can grows to 6 to 7.6 meters tall. This pseudo-stems formed by tightly packed concentric layers of leaf-sheaths, an underground rhizome and a fibrous root system. The plant growing from a corm (rhizome) produces many buds from which suckers (young shoot) develop. Rhizome or corm is an underground stem with numerous meristems (growing points) from which numerous meristems (growing points) from which the pseudo-stems, flowering and fruiting stalks, and fibrous roots arise.

Sword suckers:	small pseudo-stems (30.48 cm – 121.92 cm tall) with narrow leaves. Sword suckers will develop into fruitful pseudo-stems at maturity.
Water suckers:	small pseudo-stems (30.48 cm – 121.92 cm tall) with broad leaves. Water suckers are not well attached to the rhizome and generally produce weak plants and less fruit than sword suckers.
Peepers:	very small pseudo-stems (2.54 cm – 30.48 cm tall) that develop into either sword or water suckers.

The banana leaves consists of a long, tube like structure called a sheath, a stout petiole (leaf stalk) and a lamina blade. Leaves are spirally arranged and may grow to 2.7 meters long and 60 cm wide and each plant has 8 to 12 leaves. The tight packing of numerous sheaths that fuse at petiole bases forms the pseudo-stem. One pseudo-stem may have over 40 leaves during its lifetime.

Plants have numerous (200–500) fibrous roots. In well drained, deep, and fertile soils, roots may extend 1.5 m deep and 4.9 m laterally. In dry, shallow, or rocky soils, roots of Musa may not compete well; otherwise, Musa is an average to good competitor.

The flower of the banana also known as “Banana blossom” or “Banana heart”. Because of the banana is a monoecious plant, the flower is inflorescence that contains male flower at the tip, several sterile flowers and female flowers behind. The female flowers are produced further up the stem and they produce the actual fruit without requiring fertilization. The flowers spring in great spikes from the center of the crown of leaves and are arranged in whorl-like clusters along the spike. The banana inflorescence (flowering stalk) is produced 10 to 15 months after planting, by this time 26 to 32 leaves have been produced. The process of banana flowering is called shooting. The banana inflorescence shoots out from the heart in the tip of the stem, is at first a large, long oval, tapering, purple-clad bud. As it opens, the slim nectar-rich, tubular, toothed, white flowers appear. They are clustered in whorled double rows along the floral stalk, each cluster covered by a thick, waxy, hood like bract, purple outside and deep red within. The flowers occupying the first 5 – 15 rows are female. In the edible cultivars, the rapidly growing ovaries develop parthenocarpically (without pollination) into clusters of fruits, called “hands”.

Cultivated varieties are typically seedless. When seeds are present, they vary among species in shape and morphology. Seeds of Musa balbisiana, parent of many commercial edible banana varieties, are dark brown, ovoid, about 4 mm (0.2 in) long, with a conspicuous white, powdery endosperm.

The banana fruit technically is a berry, seedless (parthenocarpic) sterile triploid and some are fertile and can set seed. Musa fruits are variable in size, shape, and color. They are generally elongate-cylindrical, straight to strongly curved, 3–40 cm long, and 2–8 cm in diameter. The fruit apex is important in variety identification; it may be tapered, rounded, or blunt. The skin is thin and tender to thick and leathery, and silver, yellow, green, or red in color. Inside the ripe fruit, the flesh ranges from starchy to sweet, and in color from white, cream, yellow, or yellow-orange to orange (see picture below).

The actual skin is the epidermis and aerenchyma which varies in thickness, the endocarp is a thin layer while the mesocarp is the major edible part of the fruit. Some varieties have a thin peel and are more susceptible to damage in transport, whereas others have a comparably thicker peel (the Fe‘i variety ‘Karat’ and others, for example).
The banana fruit grow in hanging clusters, with up to 20 fruits to a tier (called a hand), and 3–20 tiers to a bunch. The whole hanging clusters is known as a bunch and can weigh from 30–50 kg. A banana fruit averages 125 g and the edible part contains, on the average, 75 percent water, 21 percent carbohydrate, and about 1 percent each of fat, protein, fiber (Manila hemp), and ash. Other parts of the plant abound in fiber, which can be used in the manufacture of paper and cordage. Each individual fruit (known as a banana or ‘finger’) has a protective outer layer (a peel or skin) with a fleshy edible inner portion. Typically, the fruit has numerous strings (called ‘phloem bundles’) which run between the skin and inner part. The fruit turns from deep-green to yellow or red and may range from 6.4 cm to 30 cm in length and 1.9 cm to 5.0 cm in width, and from oblong, cylindrical and blunt to pronouncedly 3-angled, somewhat curved and hornlike. The fruit of the plantain, or cooking banana, is larger, coarser, and less sweet than the kinds that are generally eaten raw. Fruits mature in 90 to 120 days after flowers first appear. This maturation day depend on season of planting and types of cultivar. Plantain and banana production cycles are around 16-20 months. A stalk bears only once, dies down, and is replaced by sprouts, two or three of which are allowed to bear fruit.

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