The biology of the citron (Citrus medica L., Rutaceae-Aurantioideae-Aurantieae), its hybrids and their allies

The biology of citrus is briefly reviewed, pointing up how surprisingly little is known of pollination and dispersal in wild species. The classification of the citron, Citrus medica, in modern science is set out in a historical context: its taxonomic relationships in the light of the evolution of the genus Citrus and the citron’s role in the origin of major citrus crops as well as the importance of the etrog citron in the traditional Jewish Tabernacles festival are outlined. The global threat to the citron and all other citrus from the bacterial disease, huanglongbing, is explained. As an aid to understanding the much-confused citrological literature, the formal taxonomy of the citron is presented in an Appendix, complete with a nomenclatural account of those commercial crops which have citron in their makeup; for example, the Rangpur lime (a rough lemon) is Citrus × otaitensis (syn. C. × volcameriana, C. × jambhiri).