A group of international researchers led by University of Florida's Fred Gmitter has traced the orange back 5 million years to two wild citrus species from southeast Asia.
Gmitter, a citrus geneticist based at the Citrus Research and Education Center in Lake Alfred. led the group that analyzed the genome sequences of 10 diverse citrus varieties.
Knowing the ancestry of citrus, the researchers to develop new varieties that are more resistant to disease and environmental stress as well have better flavor and health benefits, according to a news release.
The group looked at sweet and sour oranges along with several mandarin and pummelo varieties.
Nearly all commercial citrus trees are produced by grafting a scion onto a rootstock.
The system brings trees into production more quickly then own-root. But the trees also are almost identical to each other, so if one is susceptible to a disease, they all are.
Citrus was first domesticated in southeast Asia before spreading throughout Asia, Europe and the Americas via trade.
One of the two wild species—Citrus maxima—evolved into today's pummelo, the largest citrus fruit.
Mandarins were found to be genetic mixes of two species—Citrus reculata, the ancestral mandarin species) and pummelo.
Sweet orange, the most widely grown citrus variety, is a complex hybrid, with parentage including mandarin and pummelo.
The U.S. Department of Energy's Joint Genome Institute, Genoscope in France, the Institute for Genomic Applications in Italy, and 454 Lifge Sciences—a Roche company—contributed to the citrus genome project.