Lumia (citrus)
A recent genomic analysis of several species commonly called 'lemons' or 'limes' revealed that the various individual lumias have different genetic backgrounds. The 'Hybride Fourny' was found to be an F1 hybrid of a citron- pomelo cross, while the 'Jaffa lemon' was a more complex cross between the two species, perhaps an F2 hybrid. The Pomme d'Adam arose from a citron-micrantha cross, while two other lumias, the ‘Borneo’ and ‘Barum’ lemons, were found to be citron-pomelo-micrantha mixes.
Citron
Despite the wide variety of forms taken on by the fruit, citrons are all closely related genetically, representing a single species. Genetic analysis has shown known cultivars to divide into three clusters, a Mediterranean cluster thought to have originated in India, and two clusters predominantly found in China, one representing the fingered citrons, and another consisting of non-fingered varieties.