Exploiting a genetic quirk in potatoes may cut fertiliser needs
A GENE that controls when potato plants form their tubers also limits nitrogen uptake, scientists have discovered.
The findings, described in New Phytologist, could lead to the development of potato varieties that require less fertiliser.
Potatoes, native to the Andes, originally grew tubers only during winter as a way to store nutrients, taking cues from the shortening of the days. The plants therefore faced a significant challenge when introduced to Europe in the 16th Century. Shorter winter days came along with freezing temperatures that killed the plants before they could grow large potatoes.
Eventually, a natural genetic mutation in the gene StCDF1, which controls tuber growth, helped the potato plants adapt to grow tubers any time and much farther north. The plants no longer needed seasonal cues.
Researchers studying StCDF1 to understand how it regulates the plant’s response to the daylight cycle found that it works like a switch, activating certain genes while turning others off. But they were surprised to find that it can switch on and off genes essential for nitrogen uptake, says Maroof Ahmed Shaikh, a plant molecular biologist at the Centre for Research in Agricultural Genomics in Barcelona. Crucially, StCDF1 shuts off the production of an enzyme called nitrate reductase, which breaks down nitrate molecules so they can be used by the plant.
This discovery reveals that the genetic tweak that allowed potatoes to become a global staple food also made the plants more fertiliser-hungry.
To test if tweaking this gene would affect nitrogen uptake, the researchers grew potato plants with a disabled StCDF1 gene in a low-nitrogen environment — about 400 times less than typical soil — and studied how they fared compared with normal potato plants. The StCDF1-deficient plants could not grow tubers, but they produced bigger leaves and longer roots despite the lack of nitrogen.
The Andean varieties probably had a less active StCDF1 gene and could grow better with less nitrogen, the team explained in an interview with Science News.
However, it’s the more active form of StCDF1 that’s present in all the commercial potato varieties grown worldwide. The trade-off: The staple crop is bad at assimilating nitrogen, says plant biologist Salomé Prat, of the Centre for Research in Agricultural Genomics.
“It leads farmers to use more fertiliser than the plant can absorb. When it rains, this excess fertiliser goes to groundwaters, polluting them,” she said.
The researchers plan to use gene-editing techniques to tweak the gene that produces the nitrate reductase enzyme, so it’s not repressed by StCDF1. The team has conducted experiments showing that this is theoretically possible. This same goal could be achieved using traditional breeding, crossing farm potatoes with wild or traditional varieties that naturally have altered nitrate reductase genes.
Stephan Pollmann, a plant biologist at the Centro de Biotecnología y Genómica de Plantas in Madrid, said nitrogen uptake is one of the major obstacles in agriculture.
“Beyond being scientifically interesting, the fact that this is in potato, a real crop grown worldwide that is essential to food security, makes this finding potentially a ‘smasher’,” he said. “If you can improve the nitrate assimilation, so the nutrition of the plant, which will in consequence give you bigger tubers, this is super important.”
Source: Science Direct Photo: Ahmed Shaikh
