A paper, published in ''Nature'' on February 7, describes the origin, evolution and domestication of citrus fruits.

When life gives you lemons, blame the Himalayas, as they are the birthplace of all the citrus fruits of the world.

Genomic (DNA study), phylogenetic (study of evolution) and bio-geographic (study of migration and distribution of species through time) studies have now proved that all citrus species available today came from the south-east foothills of the Himalayas, specifically the eastern area of Assam, northern Myanmar and western Yunnan in China.

An international team of over 15 scientists studied 60 diverse species of citrus, including lemons, oranges and grapefruit, and concluded that the fruit fundamentally had just three ancestors. “It is like creating an immense jigsaw puzzle that overlaps to some degree, and then assembling these pieces into larger groups, and assembling the larger groups into even larger parts of the genome,” said Frederick Gmitter from the Citrus Research and Education Centre, University of Florida, in a release.

The paper, published in Nature on February 7, describes the origin, evolution and domestication of citrus fruits. They noted that a fossil specimen from Yunnan that dates back to about 8 million years ago has similar traits to modern ones.

Migration of the lemons

During the late Miocene Epoch, about 11 to five million years ago, as warm climate prevailed, the fruits slowly spread across the globe.

“Our analysis establishes a relatively rapid Asian radiation of citrus species in the late Miocene, a period coincident with an extensive weakening of monsoons and a pronounced climate transition from wet to drier conditions. In south-east Asia, this marked climate alteration caused major changes in biota, including the migration of mammals and rapid radiation of various plant lineages,” says the report.

During the early Pliocene (5 to 2 million years ago) and Pleistocene (2 million to 10,000 years ago) many citrus varieties diversified and hybrids were produced. By studying more about the pure and mixed species, researchers aimed to create a complete genealogy of the fruits and how their domestication and commercialisation started.

The report says that this study provides “a new evolutionary framework for the genus Citrus”.

“By improving the...understanding of our genetics and breeding knowledge base, [it can open] exciting new possibilities in genetic improvement,” Prof. Gmitter said. “And as citrus breeders, our goals have always included improvements in characteristics that benefit not only producers, but consumers as well.”


Source: February 10, 2018, The Hindu