GHENT — A study led by Ghent University plant biologist Yves Van de Peer found that whole genome duplication events in flowering plants clustered during periods of environmental turmoil over the last 150 million years. One such clustering occurred about 66 million years ago, at the time of the asteroid impact that darkened the skies and led to widespread extinctions.

The research team gathered 470 sequenced flowering plant genomes, including wild species and agricultural crops from across the world. The team scanned the DNA of these genomes for repeated gene suites as evidence of ancient whole genome duplication events, and used the fossil record to date when each event occurred.

Polyploidy is the condition in which an organism has more than two sets of chromosomes in every cell, also known as whole genome duplication. Many plants, including multiple species of bananas, have more than two sets of chromosomes.

"Once in a while something goes wrong, and you end up basically with a new cell with twice the amount of DNA than a normal plant cell," Van de Peer said. "These whole genome duplications do not occur randomly. They are clustered in time," he added.

Polyploid plants often have a competitive advantage under environmental stressors such as prolonged changes in temperature or reduced light levels because they have additional genes for photosynthesis. Most polyploid plants are eventually outcompeted by plants with fewer chromosome sets due to slower cell division and increased mutation errors. Descendants of polyploid plants often lose extra chromosome copies over time but retain molecular evidence of ancient whole genome duplication events in their DNA.

Sandra Pitta, a plant biotechnologist at CONICET, said the findings could inform work on crop resilience. "The paper really is very rigorous," Pitta said. "If polyploidism helps them resist more different types of stresses, well, that is really useful to me," she added.