Scientists Sequence Genomes of 60 Citrus Varieties to Draw Up Family Tree and Understand Disease Response

Citrus is one of the world's best-loved fruit, but the crop has been beset by Huanglongbing (a.k.a., citrus greening), an infectious disease destroying whole orchards. Researchers are now using genomics to better understand how citrus varieties respond to disease and other stresses.

A global team of scientists sequenced the genomes of 60 citrus varieties to draw up a family tree and investigate the genetic diversity and evolutionary history of citrus. The team led by researchers at the Joint Genome Institute (JGI), the Instituto Valenciano de Investigaciones Agrarias in Spain, and the Citrus Research and Education Center of the University of Florida, has now proposed a revised genealogy of the major citrus cultivars and traced the origin of citrus back to the Himalayan foothills.

The study states that citrus originated in an area limited by Eastern India, Northern Myanmar, and Western Yunnan during the late Miocene. The first attempts at domesticating these fruits are thought to be by asexual propagation through apomictic seeds and the deliberate selection for specific traits which generated a complex network of relatedness among cultivated citrus that is recorded in the genomes. Southeast Asia has long been considered the birthplace of citrus, and the citrus plants are thought to have then migrated across Asia, reaching Australia around 4-5 million years ago, during the early Pliocene period.

For more information, visit JGI.