Banana is a crop which has dual propagation abilities, asexual through suckers and sexual through seeds. Seed propagation is general in wild species that are diploid and go through normal meiosis, seed set and fertilization. The extent of seed set, dormancy and germinability relies on the species. In Ensete, only other genus of the Musaceae, seed propagation is only means of perpetuation as sucker production is not present. Seeds are normally black to brown in color, 3-7 cm in diameter, triangular or round in shape, and mostly compacted in appearance. Fruits of undomesticated species are inedible, being complete of seeds that are covered in thin mucilaginous pulp. All cultivated commercial bananas are sterile and triploid, excepting a small number of parthenocarpic AB and AA diploids. Sucker propagation is only natural means of its perpetuation; artificial processes of propagation are macropropagation and micropropagation.
There are two categories of suckers, such as water suckers and sword suckers. Water suckers are less vigorous, small in size, emerge in clumps and broad leaved. Sword suckers have a well developed base, narrow leaf blades and pointed tip. Natural regeneration of the cultivated bananas with suckers is very slow process due to hormone-mediated apical supremacy of the mother plant. A banana plant produces only 6-20 suckers throughout its life span of 10-14 months. For speed up the rate of propagation, suckers with cut rhizomes or growing buds called 'peepers' and 'bits' are used. A number of good bits, every with a centrally located germinating eye can be reduced from an unbunched rhizome following trimming the roots. Selection of proper mother plant for growing new propagules either through in vitro or in vivo methods is significant. About one kg uniformly shaped bits or rhizomes, well-trimmed around the raising sprout are the best beginning material. Although instant planting is ideal, in some parts of the India rhizomes are dried in the sun for 2-3 days after pralinage and paring treatment (trimmed of the all roots, sprinkled with nematicide and dipped in the mud slurry) and stored in shade for seven days before planting.
Macropropagation is an excellent choice for producing low cost planting material. It is a simple process because of the simplicity of multiplication saves cost of the producing planting matter and has the possibility of producing 45-60 shoots per sucker during 4-5 months. Macropropagation is attained by two processes and could be implemented either in the nursery (also called ex-situ condition) or in the field conditions (also called in situ condition). It involves decortication, decapitation and hardening.
The Plant of 4-6 month old is headed back, pseudo stem is removed and incisions or cross cuts are made on the raising meristem so that stimulate the generation of lateral buds. This process results in the generation of 10-16 uniform shoots per plant within a short duration of time and is highly appropriate for marginal and small farmers whose needs of planting material are comparatively small. Suckers of selection varieties can be kept in a nursery either in a big concrete pot or in sawdust bed. The primary planting material should preferably be qualified as multiplied at farm level and virus free under a pest proof net house.
The sword sucker is removed transversely 2 cm on top of the collar region and after that the apical meristem is cut leaving a cavity of 4 cm depth and 2 cm diameter. it is done to overcome apical dominance.
The lateral sprouts of 7-12 cm length are moved to pro-trays having equal parts vermiculite of and cocopeat and after adequate watering left in a shade net at 80-90 % humidity. Sprouts are generally maintained in pro-trays for a time of 2 to 3 weeks and transferred to polythene bags of thickness of 120 gauge and size 6'x 4' for secondary hardening.
Advantages of Micropropagation for Banana Planting
Micropropagation is the process of quickly multiplying the stock plant material to generate a big number of progeny plants within aseptic conditions utilizing modern plant tissue culture techniques. Application of micropropagation in banana has different advantages, such as, rapid multiplication, production of disease free planting material, season independent production, high returns etc.
The multiplication rate in banana is limited to 5-20 suckers per plant throughout its development period, which makes it hard to obtain adequate amount of planting matter of a clone of selection. Micropropagation facilitates generation of big number of plantlets or unit time, thus assisting in rapid introduction and distribution of new varieties.
The rapid multiplication mechanism makes sure that a small number of mother plants are needed for growing large number of the progeny plants. These mother plants can be preserved with required care at a small cost.
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