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Seedless Fruits

Parthenocarpy and Parthenogenesis
Parthenocarpy refers to the development of the fruit (ovary) without fertilization whereas Parthenogenesis refers to the development of an egg cell (seed) without fertilization. The fruits that develop parthenocarpically are typically seedless. The triploid plants containing 3 sets of chromosomes rather than 2 sets in its cells are sterile and producing seedless fruits of Horticultural importance. The triploid seeds can be produced by crossing a fertile tetraploid (4n) plant with a normal diploid (2n) plant.
Seedless watermelon: To get the seedless watermelon fruits from sterile triploid watermelon plants both fertile diploid and sterile triploid seeds of
watermelon are sown in same plots. The male flowers on the diploid plant pollinate flowers of sterile triploid plants but does not fertilize. The pollination requires inducing seedless fruit development from triploid watermelon plants parthenocarpically with out fertilization.
Seedless Banana: The banana fruit developed parthenocarpically from sterile triploid hybrids (Musa paradisiaca) is seedless. Tha M. pasadisiaca is a complex hybrid obtained from two fertile  diploid Asian species, M. acuminata (sugary) and M. balbisiana (starchy). The hybrid between M. acuminata (AA genomes) and M. balbisiana (BB genomes) produced either diploid hybrids (AB) or triploids (AAB, ABB etc.). It seems that M. acuminata migrated to the area of M. balbisiana followed by non-reduction to produced triploids.  Common cultivated banana are triploid (3n) with three sets of Chromosomes representing AAB, ABB or another 3-leatters combination of A,s and B,s where A and B representing one haploid (n) set of Chromosomes from diploid M. acuminata  (AA) and diploid M. balbisiana (BB), respectively. The homologous Chromosomes make pair with each other during synapsis of prophase I under normal meiosis to form haploid (n) gametes. In sterile triploid banana one set of Chromosome A or B has no homologous set to make pair during meiosis resulting unviable gametes formation. Subsequently seedless banana fruits develop parthenocarpically from unreduced gametes (2n+n) without fertilization. The aborted ovules inside the banana fruit may appear like tiny black dots.
M. acuminata (AA) X M. balbisiana (BB) = M. paradisiacal (AB or AAB, ABB etc)
(Fertile Asian banana) X (fertile Asian banana) = (diploid hybrid or sterile triploid)

Seedlessness in Grape: The gibberellic acid (GA3) is used to induce seedlessness in grape cultivars like ‘Thompson seedless in which ovaries mature into berry with failure of the ovules to develop. The berries become larger with longer internodes for better air circulation and lesser susceptibility to fungal diseases and rotting. The ‘Thompson seedless’ grape is not parthenocarpic fruit because fertilization takes place but ovules fail to develop into seeds.

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