Dr Colin Eady of Crop & Food Research in New Zealand and his collaborators in Japan have been testing tearless onions in the laboratory and have presented their results so far to the 5th International Symposium on Edible Alliaceae, in The Netherlands.

Dr Eady describes “tearless” onions as being in the developmental stages but if the research progresses well, would like to see them become the household and industry norm within the next decade.

“We have been using a gene-silencing technology, called RNAi, developed by Dr Peter Waterhouse at CSIRO in Australia, that allows us to retarget the plant’s own natural regulation system without expressing foreign proteins in the plant,” Dr Eady says.

“Through RNAi, genes can be specifically shut down or turned off. By shutting down the lachrymatory factor synthase gene, we have stopped valuable sulphur compounds being converted to the tearing agent, and instead made them available for redirection into compounds, some of which are known for their flavour and health properties.”

Dr Eady says the research team has been unable to induce tearing by crushing their model tearless onions.

“What we have now is a truly unique germplasm with a unique trait. We can home in and study what the consequences of this one effect are. We can detect differences in sulphur compounds known to be involved in flavour and health and actually measure them and assign to them a role.”

Dr Eady says although the “tearless onion” is an exciting project, he is most interested in sustainable and efficient production and will want to be sure that the onions he is working on are also capable of being grown in an efficient manner. “We have a burgeoning population to feed, and with climate change and other challenges, available resources are being reduced. The gene silencing system can also be used to combat virus diseases and biotechnology in general can help us produce more robust crops.”

Dr Eady says in many countries onions already contribute a significant proportion of the daily fibre requirements of the populations. “They are such a versatile and nutritious vegetable, that if we can manage to get more people cooking and eating fresh onions, then that has got to be a positive outcome.”

Further information is available in the International onion trade journal Onion World, in the last issue published in 2007.