Study of plant mutation rate offers insights for breeding

Research lead

Scientists at the Max Planck Institute for Developmental Biology in Tübingen, Germany, and Indiana University in Bloomington have measured directly for the first time the speed with which new mutations occur in plants. The findings shed new light on a fundamental evolutionary process, explaining, for example, why resistance to herbicides can appear within just a few years.

“While the long term effects of genome mutations are quite well understood, we did not know how often new mutations arise in the first place,” said Detlef Weigel, director at the Max Planck Institute in Germany. It is routine today to compare the genomes of related animal or plant species. Such comparisons, however, ignore mutations that have been lost in the millions of years since two species separated.

The teams of Weigel and his colleague Michael Lynch at Indiana University therefore wanted to scrutinise the signature of evolution before selection occurs. To this end, they followed all genetic changes in five lines of the mustard relative Arabidopsis thaliana that occurred during 30 generations. In the genome of the final generation they then searched for differences to the genome of the original ancestor.

The results show that in sufficiently large populations, every possible mutation in the genome should be present. Thus, plant breeders should be able to find any simple mutation that has the potential to increase yield or make plants tolerate drought better.

Finding these among all the unchanged siblings remains nevertheless a daunting task. On the other hand, the new findings explain why weeds become quickly resistant to herbicides. In a large weed population, a few individuals might have a mutation in just the right place in the genome to help them withstand the herbicide. “This is in particular a problem because herbicides often affect only the function of individual genes or gene products,” says Weigel. A solution would be provided by herbicides that simultaneously interfere with the activity of several genes.