Citrus origin and Evolution

The genus Citrus, the most cultivated fruit crop worldwide, includes an elusive number of species of diverse fruit trees. Through genomic, phylogenetic and biogeographic analyses of 40 accessions, we identified ten natural citrus species and propose that citrus diversified during late Miocene through a rapid Southeast Asian radiation correlating with a dramatic weakening of the monsoons. A second radiation enabled by migration across the Wallace line gave rise to the Australian limes in the early Pliocene. Further identification and analyses of hybrids and admixed genomes allowed the elucidation of the genealogy of major citrus commercial cultivars. Among mandarins and sweet orange, we find an extensive network of relatedness that illuminates the domestication of these groups. Widespread pummelo admixture among these mandarins and its correlation with fruit size and acidity indicates a plausible role of pummelo introgression in the selection of palatable mandarins. This work provides a new evolutionary framework for the genus Citrus.