Citrus taxonomy

Citrus taxonomy refers to the botanical classification of the species, varieties, cultivars, and graft hybrids within the genus Citrus, subgenus Papeda, and related genera, found in cultivation and in the wild.

Citrus taxonomy is complex. Cultivated citrus are derived from various forms of old citrus species found in the wild. Some are only selections of the original wild types, while others are hybrids between two or more ancestors. Citrus plants hybridize easily between species with completely different morphologies, and similar-looking citrus fruits may have quite different ancestries.

Most hybrids express different ancestral traits when planted from seeds (F2 hybrids) and can continue a stable lineage only through vegetative propagation. Others do reproduce true to type via nucellar seeds in a process called apomixis. Many different-looking varieties are nearly genetically identical, and differ only by a bud mutation. Some differ only in disease resistance.

Clear genetic lineages are very important for breeding improved cultivars.

Interbreeding seems possible between all citrus plants, and between citrus plants and some plants which may or may not be categorized as citrus. The ability of citrus hybrids to self-pollinate and to reproduce sexually also helps create new varieties.

The four core ancestral citrus taxa are citron (C. medica), pummelo (C. maxima), mandarine (C. reticulata), and papeda (C. micrantha).

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