20/06/2017
The watermelon is a large annual plant with long, weak, trailing or climbing stems which are five-angled (five-sided) and up to 3 m (10 ft) long. Young growth is densely woolly with yellowish-brown hairs which disappear as the plant ages. The leaves are large, coarse, hairy pinnately-lobed and alternate; they get stiff and rough when old. The plant has branching tendrils. The white to yellow flowers grow singly in the leaf axils and the corolla is white or yellow inside and greenish-yellow on the outside. The flowers are unisexual , with male and female flowers occurring on the same plant ( monoecious ). The male flowers predominate at the beginning of the season; the female flowers, which develop later, have inferior ovaries. The styles are united into a single column. The large fruit is a kind of modified berry called a pepo with a thick rind ( exocarp ) and fleshy center ( mesocarp and endocarp). [1] Wild plants have fruits up to 20 cm (8 in) in diameter, while cultivated varieties may exceed 60 cm (24 in). The rind of the fruit is mid- to dark green and usually mottled or striped, and the flesh, containing numerous pips spread throughout the inside, can be red or pink (most commonly), orange, yellow, green or white. [2][3]
History
The watermelon is a flowering plant thought to have originated in southern Africa, where it is found growing wild. It reaches maximum genetic diversity there, with sweet, bland and bitter forms. In the 19th century,
Alphonse de Candolle [4] considered the watermelon to be indigenous to tropical Africa. [5] Citrullus colocynthis is often considered to be a wild ancestor of the watermelon and is now found native in north and west Africa. However, it has been suggested on the basis of chloroplast DNA investigations that the cultivated and wild watermelon diverged independently from a common ancestor, possibly C. ecirrhosus from Namibia . [6]
Evidence of its cultivation in the Nile Valley has been found from the second millennium BC onward. Watermelon seeds have been found at Twelfth Dynasty sites and in the tomb of Pharaoh Tutankhamun. [7]
In the 7th century, watermelons were being cultivated in India, and by the 10th century had reached China, which is today the world's single largest watermelon producer.
Moorish invaders introduced the fruit into Europe and there is evidence of it being cultivated in Córdoba in 961 and also in Seville in 1158. It spread northwards through
southern Europe , perhaps limited in its advance by summer temperatures being insufficient for good yields. The fruit had begun appearing in European herbals by 1600, and was widely planted in Europe in the 17th century as a minor garden crop. [2]
European colonists and slaves from Africa introduced the watermelon to the New World . Spanish settlers were growing it in Florida in 1576, and it was being grown in Massachusetts by 1629, and by 1650 was being cultivated in Peru , Brazil and Panama , as well as in many British and Dutch colonies. Around the same time, Native Americans were cultivating the crop in the Mississippi valley and Florida. Watermelons were rapidly accepted in Hawaii and other Pacific islands when they were introduced there by explorers such as Captain James Cook . [2]
Seedless watermelons were initially developed in 1939 by Japanese scientists who were able to create seedless
triploid hybrids which remained rare initially because they did not have sufficient disease resistance . [8] Seedless watermelons became more popular in the 21st century, rising to nearly 85% of total watermelon sales in the United States in 2014.
