Legume plants, like pea, broad bean, soya bean, clover and cowpea, team up with soil bacteria to convert, or ‘fix’, the nitrogen present in air – meaning that, unlike most crops, they do not need fertilisers.

But why do legumes have this superpower when most other plants do not? A global study led by scientists at the James Hutton Institute and the University of Zurich, funded by the Engineering Nitrogen Symbiosis for Africa (ENSA) project, has been exploring the origin of nitrogen fixation in the legume family.

The scientists examined 128 legume species and produced a genetic tree of these plants, and found that the ability to fix nitrogen was directly related to the intimacy of each species' relationships with the rhizobia around its roots.

Dr Euan James, an ecological scientist at the James Hutton Institute and co-author of the study, said: “This is one of the most important scientific papers of my career.

“Tracing the origins of legumes’ ability to fix nitrogen and maintain this partnership will allow future research teams to develop more resilient, environmentally friendly crops, allowing for enhanced food security for an increasing global population.”

The study, catchily entitled 'The innovation of the symbiosome has enhanced the evolutionary stability of nitrogen fixation in legumes', co-authored by Sergio M. de Faria et al, has been published by New Phytologist.