Orange is the fruit of Citrus in Rutaceae. It is also known as sweet orange to distinguish it from the related citrus aurantium, known as bitter orange. Asexual reproduction of sweet orange (reproduction through the blastocyst of the nucleus). All kinds of sweet orange are produced by mutation.

Orange is a hybrid between Citrus maxima and Mandarin. Its genes are grapefruit about 25% and Mandarin about 75%. However, it is not a simple backcross BC1 hybrid, but a multi generation hybrid. The chloroplast gene, and thus the maternal line, appears to be grapefruit. The whole genome of sweet orange has been sequenced. It is reported that the percentage of grapefruit genes varies from 50% to 6%.

Sweet orange was mentioned in Chinese literature in 314 BC. Since 1987, orange tree has been found to be the most planted fruit tree in the world. In tropical and subtropical climates, orange trees are widely cultivated for their sweet fruits. The fruit of orange tree can be eaten fresh or processed into juice or pericarp. As of 2012, sweet orange accounted for about 70% of citrus production.

In 2013, the output of oranges in the world was 71.4 million tons, the highest in Brazil, Florida and California.

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