Citreae

Citreae is a tribe of the citrus family Rutaceae, in the subfamily Aurantioideae. It comprises several genera that are closely related to the cultivated citrus trees, most notably Citrus, and includes other genera such as Poncirus and Fortunella, among others. Native to Asia and Australia, many species are adapted to tropical and subtropical climates and have been widely introduced around the world through cultivation.

Members are typically evergreen shrubs or small trees, often with thorns; leaves are usually simple with winged petioles; flowers are white and fragrant; fruits are hesperidia, commonly known as citrus fruits, with juice-filled vesicles.

Taxonomy and evolution: The circumscription of Citreae has changed with molecular phylogenetics. Citrus remains central, but some authors recognize Poncirus, Fortunella, and Microcitrus as distinct but closely related lineages within Citreae or treat them as part of a broad Citrus sensu lato. Economic importance: The group includes the major commercial fruits—orange, lemon, lime, grapefruit—and related edible fruits; kumquats (Fortunella) and finger limes (Microcitrus) have additional uses; Poncirus trifoliata is widely used as a cold-hardy rootstock. The group faces major agricultural challenges from pests and diseases such as citrus greening.