Exploiting a genetic trait in potatoes could cut fertilizer needs

Potatoes are the third most consumed food worldwide and a delicious snack. But modern farm potatoes require large amounts of nitrogen in the form of nitrate fertilizers, which are costly and can be harmful to the environment.

A group of researchers has discovered that the same genetic mechanism that tells potatoes when to grow flowers and tubers (the edible part) is also a key player in the plant’s nitrogen management. The findings, described Nov. 6 in Young phytologistcould lead to the development of potato varieties that require less fertilizer, saving farmers money and reducing the environmental footprint of potato cultivation.

Potatoes, native to the Andes, originally grew tubers only during the winter as a way to conserve nutrients, taking cues from the shortening of the days. Therefore, plants faced a significant challenge when they were 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 StCDF1which controls tuber growth, helped potato plants adapt to grow tubers at any time and much farther north. Plants no longer needed seasonal signs.

Researchers who study StCDF1 to understand how it regulates the plant’s response to the daylight cycle, discovered that it works like a switch, turning certain genes on while turning others off. But they were surprised to find that it can turn genes essential for nitrogen uptake on and off, says Maroof Ahmed Shaikh, a plant molecular biologist at the Center for Research in Agricultural Genomics in Barcelona. most importantly, StCDF1 it stops 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 change that allowed potatoes to become a global staple also made plants hungrier for fertilizer.

To test whether changing this gene would affect nitrogen uptake, the researchers grew potato plants with disabilities. StCDF1 gene in a low-nitrogen environment – about 400 times less than typical soil – and studied how they fared compared to normal potato plants. of StCDF1– Deficient plants could not grow tubers, but they produced larger leaves and longer roots despite the nitrogen deficiency. “They looked happy,” says Shaikh.

Andean varieties probably had a less active one StCDF1 gene and can grow better with less nitrogen, the team explains.

However, it is the most active form of StCDF1 which is present in all commercial potato varieties grown worldwide. The trade-off: the main crop is bad at assimilating nitrogen, says plant biologist Salomé Prat, also of the Center for Research in Agricultural Genomics. “That’s a problem,” because it causes farmers to use more fertilizer than the plant can absorb, Prat says. “When it rains, this excess fertilizer goes into the groundwater, polluting it.”

The discovery opens the door to the development of potato varieties with increased nitrogen efficiency. Researchers are planning to use gene-editing techniques to adjust the gene that makes the enzyme nitrate reductase so that it is not suppressed by StCDF1. The team has conducted experiments that show this is theoretically possible. The same goal can be achieved using traditional breeding, crossing farm potatoes with wild or traditional varieties that have naturally altered nitrate reductase genes.

“Nitrogen uptake is one of the main constraints in agriculture,” says Stephan Pollmann, a plant biologist at the Centro de Biotecnología y Genómica de Plantas in Madrid, who was not involved in the new study. Beyond being scientifically interesting, the fact that this is in potatoes, a real crop grown around the world that is essential to food security, makes this finding potentially “explosive,” says Pollmann. “If you can improve nitrate assimilation, so plant nutrition, which will consequently give you bigger tubers, that’s very important.”