ABSTRACT
The genus Citrus comprises hundreds of species, varieties, and hybrids issued from natural or human-controlled crossbreeding. Conventional fruits such as oranges, lemons, grapefruits, pummelos, limes, mandarins-tangerines, and yuzu are produced for commercial purposes. In addition, new hybrids with increased phytosanitary and organoleptic performances have been created. At the same time, there exists a category of unusual citrus fruits, either growing wild, limited to local interest, or with minor sensory value that are often used as rootstocks for trees with greater tolerance to extreme temperatures, resistance to diseases, and better yield and quality of fruits. Lawrence (2002) has reviewed a series of these less common Citrus species: Citrus aurantium L. var. myrtifolia, C. clementina, C. grandis, C. hystrix, C. jambhiri, C. junos, C. madurensis, C. medica, C. medica var. ethrog, C. medica var. sarcodactylis, and C. unshiu. Meanwhile, the volatile composition of many more of these interesting members of the Citrus genus has been investigated and will be discussed in this chapter. Recently, phylogenetic studies of plants of the genus Citrus and the related Fortunella, Microcitrus, Poncirus, and Eremocitrus have indicated that these genera have very similar genetic systems and can therefore all be classi ed in the genus Citrus (Mabberley, 1998; de Araújo et al., 2003). Some of these species will also be included in this review.
