Citrus (genus)

Genus of plants that includes the citron, lemon, lime, orange, grapefruit, tangerine, shaddock, and their many varieties, most yielding pulpy fruits covered with fairly thick skins. The genus is believed to have originated in southeast Asia; citrus has been cultivated in an increasingly large area since ancient times. The precise number of natural species is unclear and their taxonomy is complex because many of the named species are clonally propagated hybrids. There is genetic evidence that even some wild breeding species are of hybrid origin: cultivated citrus may be derived from as few as four ancestral species.