The breeding of new, high-quality citrus cultivars depends on dependable information about the relationships of taxa within the tribe Citreae; therefore, it is important to have a well-supported phylogeny of the relationships between species not only to advance breeding strategies, but also to advance conservation strategies for the wild taxa. The recent history of the systematics of Citrus (Rutaceae: Aurantioideae) and its allies, in the context of Rutaceae taxonomy as a whole, is reviewed. The most recent classification is tested using nine cpDNA sequence regions in representatives of all genera of the subfam. Aurantioideae (save Limnocitrus) and numerous species and hybrids referred to Citrus s.l. Aurantioideae are confirmed as monophyletic. Within Aurantioideae, tribe Clauseneae are not monophyletic unless Murraya s.s. and Merrillia are removed to Aurantieae. Within tribe Aurantieae, the three traditionally recognized subtribes are not monophyletic. Triphasiinae is not monophyletic unless Oxanthera is returned to Citrus (Citrinae). Balsamocitrinae is polyphyletic. Feroniella, traditionally considered allied closely to Limonia (=Feronia), is shown to be nested in Citrus. The proposed congenericity of Severinia and Atalantia is confirmed. The most recent circumscription of Citrus is strongly supported by this analysis, with hybrids appearing with their putative maternal parents. The genus was resolved into two clades, one comprising wild species from New Guinea, Australia, and New Caledonia (formerly Clymenia, Eremocitrus, Microcitrus, Oxanthera), but surprisingly also Citrus medica, traditionally believed to be native in India. The second clade is largely from the Asian mainland (including species formerly referred to Fortunella and Poncirus).

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