If you gloog the two researchers mentioned, you find a Nature article (Abstract). The "new research" was published last December.

Though, judging from the abstract, no mention is made of GM crops, the Guardian article states helpfully:

Growth in crop yields inadequate to feed the world by 2050 - research | Environment | guardian.co.uk

The study's findings are also likely to fuel debate over the efficacy of genetically modified crops, which some scientists have argued may be needed in future to feed the rapidly growing global population, which is expected to reach at least 9 billion by 2050.

I wonder who pitched this to Fiona Harvey, "environment correspondent", and why she's pitching it to the Grauniad's readership.