Citrus phylogeny and genetic origin of important species as investigated by molecular markers

Citrus phylogeny was investigated using RAPD, SCAR and cpDNA markers. The g enotypes analyzed included 36 accessions belonging to Citrus together with 1 accession from each of the related genera Poncirus, Fortunella, Microcitr us and Eremocitrus. Phylogenetic analysis with 262 RAPDs and 14 SCARs indic ated that Fortunella is phylogenetically close to Citrus while the other th ree related genera are distant from Citrus and from each other. Within Citr us, the separation into two subgenera, Citrus and Papeda, designated by Swi ngle, was clearly observed except for C. celebica and C. indica. Almost all the accessions be longing to subgenus Citrus fell into three clusters, eac h including 1 genotype that was considered to be a true species. Different phylogenetic relationships were revealed with cpDNA data. Citrus genotypes were separated into subgenera Archicitrus and Metacitrus, as pro posed by T anaka, while the division of subgenera Citrus and Papeda disappeared. C. me dica and C, indica were quite distant from other citrus as well from relate d genera. C. ichangensis appeared to be the ancestor of the mandarin cluste r, including C. tachibana. Lemon and Palestine sweet lime were clustered in to the Pummelo cluster led by C. latipes. C, aurantifolia was located in th e Micrantha cluster. Furthermore, genetic origin was studied on 17 cultivat ed citrus genotypes by the same molecular markers, and a hybrid origin was hypothesized for all the tested genotypes. The assumptions are discussed wi th respect to previous studies; similar results were obtained for the origi n of orange and grapefruit. Hybrids of citron and sour orange were assumed for lemon, Palestine sweet lime, bergamot and Volkamer lemon, while a citro n x mandarin hybrid was assumed for Rangpur lime and Rough lemon. For Mexic an lime our molecular data indicated C. micrantha to be the female parent a nd C. medica as the male one.