For the first time, grafting has been made to work in monocots, a type of plant including oats, wheats, and bananas – and it might improve disease tolerance among these important crops.
A new technique for grafting plants could increase production and eliminate diseases for some of the world’s most imperiled crops, such as bananas and date palms.
Plant grafting, where the root of one plant is attached to the shoot of another, has been used in agriculture for thousands of years to improve crop growth and eradicate diseases. But it was only thought to work for one class of plants: the dicotyledons (or dicots), which includes apples, cherries, citrus fruits, tomatoes and melons.
The other major group of flowering plants – the monocotyledons (or monocots) – includes all grasses like wheat and oats, as well as other high-value crops like bananas and date palms. It had been thought impossible to graft monocots due to their lack of a tissue called vascular cambium, which helps grafts heal and fuse.
Now, Julian Hibberd at the University of Cambridge and his colleagues have found an approach that allows monocots to be grafted. They extracted a form of embryonic plant tissue from inside the monocot plant seed and applied it to the potential graft site between two monocots.
The tissue stimulated growth and fused the two plant halves together. The research team used fluorescent dyes to verify that the root and shoots had fused and could transport liquids and nutrients up and down the stem.
“I have written on the record that I thought it was near impossible. So, as a science breakthrough, it’s pretty amazing,” says Colin Turnbull at Imperial College London.
The method appeared to work on a wide range of monocot plant families, including important crops such as pineapple, banana, onion, tequila agave, oil palm and date palm. The team’s preliminary studies in the lab also suggest that the grafting of a wheat shoot to disease-resistant oat roots may protect the wheat from soil-borne disease, although it is still unclear whether this protection would be feasible in the real world.
Hibberd, who worked on the research after a proposal from his colleague Greg Reeves, was initially hesitant. “Everyone said you can’t do it, so I didn’t want [Reeves] to dedicate a PhD to trying something that everyone says you can’t do,” says Hibberd. ”It’s a beautiful thing. It’s science at its best, where you find something out even though everyone says it’s not possible, and he proved me wrong.”
The technique could be especially useful for combating disease in vulnerable species like the Cavendish banana, which forms the vast majority of the world’s supply. Unable to reproduce sexually, the Cavendish is only reproducible by cloning, meaning the crop is highly genetically uniform and so vulnerable to diseases like Panama disease, which is caused by a soil-borne fungus.
By grafting more disease-resistant stems (or rootstocks) with the banana plant, the Cavendish could avoid Panama disease.
The procedure may not be feasible for grasses like wheat and oat, as the process would have to be repeated millions of times for a single harvest. But for large plants that live for many years and generate high-value produce, like date palm or tequila agave, the method could prove to be cost-effective.
One of the most immediate uses for the procedure could be in research labs, where grafting is already used regularly to understand how dicots transport material up and down the stem.
Source: Julian Hibberd, Monocotyledonous plants graft at the embryonic root–shoot interface, Nature (2021). DOI: 10.1038/s41586-021-04247-y.
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