Editing a plant's genes is only half the battle — and for years, the second half has been the one that stumps scientists. Before a promising new trait can reach a farmer's field, researchers have to coax a handful of edited cells to grow into a whole new plant. For crops like citrus, that slow, finicky step has sometimes felt impossible. Now a team of scientists in Texas has built a tool called CRISPR-Combo that speeds that whole process up, sometimes by more than a month.
The work, published in the journal Nature Communications, comes from researchers at Texas A&M AgriLife Research, the University of Maryland and the U.S. Department of Agriculture. The system edits a plant's genes with the famous CRISPR scissors at the same time it flicks on the plant's own natural "morphogenic" genes — the ones that tell cells how to divide and grow into roots, shoots and finally a full plant.
Here's the clever part: instead of adding extra copies of growth genes from the outside, CRISPR-Combo simply turns up the versions that already sit inside the plant's own DNA ratings. "Regeneration is one of the biggest roadblocks standing between a promising gene edit in the lab and a crop variety that's actually useful to growers," said Mandadi, director of the Texas A&M AgriLife Research and Extension Center at Weslaco)Skip. "This work shows that we can coax a plant's own genes to regenerate faster and more reliably."
That matters a lot for growers. Perennial crops like citrus and poplar can take years to move through a single breeding cycle, and many high-value fruit and nut crops have stubbornly resisted lab regeneration. By using a plant's own genes instead of added hormones or extra genetic material, CRISPR-Combo offers a simpler, more scalable path.
The team couldn't just guess which genes to activate, so they screened dozens of candidates using a fast "hairy root" system that grows roots on plant cuttings without rebuilding a whole plant. In potatoes, lead author and AgriLife Research scientist Manikandan Ramasamy and colleagues tested 17 genes and found four that boosted root production; three of those also pushed shoot regeneration efficiency to 45–70%, versus about 30–35% in controls. In notoriously stubborn citrus, five of ten screened genes raised shoot regeneration to 80% or higher — up from under 60% in controls.
Then the team went further in wild strawberry and poplar, switching on two morphogenic genes at once. In strawberries, that stacked approach shortened the time to a fully regenerated, gene-edited plant by more than a month. In poplar, the double activation was even more striking: shoots regenerated in under a month with no external plant hormones at all — normally a requirement in tissue culture. Those poplar plants carried the highest rates of edited cells and grew into taller, higher-biomass plants, with no obvious defects.
The approach, the researchers believe, can be adapted to hunt for regeneration genes in other tough-to-work-with commercial crops. It's a reminder that sometimes the fastest route forward is the one that trusts a plant's own built-in strengths.