Princess Anne has said genetically-modified crops have important benefits for providing food and she would be open to growing them on her own land.
She told BBC Radio 4's Farming Today "we have to accept" the process could help production and livestock health.
Her brother, the Prince of Wales, has previously warned GM crops could cause an environmental disaster.
But Princess Anne said: "To say we mustn't go there 'just in case' is probably not a practical argument."
In an interview with the rural affairs programme to be broadcast on Thursday, the 66-year-old Princess Royal said she saw no problem with modifying crops if it improved their ability to grow.
"Gene technology has got real benefits to offer," said Princess Anne, who is a working farmer and patron of nearly 50 countryside organisations.
She said gene technology would "maybe have an occasional downside but I suspect not very many".
She added that she would be happy to use GM for crops and livestock on her own farming estate, Gatcombe Park in Gloucestershire.
"We grow some very good plants here remarkably easily," she said. "I don't see the problem in saying 'is there something we could do to improve their abilities?'"
Princess Anne talked about the difficulties she has experienced developing rare-breed cattle, adding long-term investment to develop suitable genetic modification to help improve their health would be a "bonus".
Farming Today has been speaking to a number of leading figures about the future of the environment and farming post-Brexit.
Deep-seated opposition has seen just one GM crop commercially cultivated in the EU over the past 20 years.
In the UK, as in many other countries, there have been several trials, including GM wheat, but nothing has ever been licensed.
However, that could all change as in the House of Commons last autumn, farming minister George Eustice indicated the government was open to re-examining its position with GM crops after the UK leaves the EU.
Princess Anne first entered the debate in 2000, when she said it was a huge oversimplification to say all farming ought to be organic.
Her position appears at odds with her brother's long-standing and vociferous opposition to GM crops.
The Prince of Wales is a royal patron of the Soil Association, which has campaigned against GM crops and ingredients in human and animal food.
He has argued that GM crops damaged the Earth's soil, describing them in 2008 as an experiment "gone seriously wrong".
Speaking from Buckingham Palace, Princess Anne told Farming Today that "GM is one of those things that divides people".
She added: "Surely, if we're going to be better at producing food of the right value, then we have to accept that genetic technology... is going to be part of that.
"How you define what is harmful or what is good seems to be rather more difficult."
In the interview, she also discussed biofuels, the use of science in farming and what kind of subsidies could help farmers in the future.
Hear Princess Anne on BBC Radio 4's Farming Today on Thursday 23 March from 05:45 GMT.