Potatoes plants are known for disliking high temperatures. During heat periods, potato plants form significantly lower numbers of tubers or sometimes none at all, but biochemists at the Friedrich-Alexander Universität Erlangen-Nürnberg (FAU) have discovered the reason why.

The reason is this: if the temperature rises, a so-called small RNA blocks the formation of tubers. Now the researchers at the FAU has successfully switched off this small RNA and have produced potato plants that are more resistant to high temperature, which is an important contribution to securing crop yields in the future in the view of climate change. Their complete findings were recently published in the journal Current Biology.

Along with maize, rice, wheat, and cassava, potatoes are one of the most important staple foods worldwide. The highest yields can be gained at moderate temperatures, which means around 21⁰ C during the day and 18⁰ C at night. At these temperatures and at the correct day length, a protein that induces the formation of tubers called SELF-PRUNING 6A (SP6A) is formed. This triggers tuber formation in the plant to prepare it for colder periods. However, if the temperature is very warm, as is the case in the laboratory led by Prof. Dr. Uwe Sonnewald’s team at FAU, who set the temperature to 29 degrees during the day and 27 degrees at night, the plants switch to a kind of growth program where they form more green shoots and leaves and hardly any or no tubers. In addition, the few tubers that are formed contain less starch and germinate more quickly, which means they are not as nutritious and rot more quickly.

“Up to now, the mechanism that prevents tuberization at high temperatures was not known,” notes Prof. Dr. Sonnewald chair of biochemistry at FAU. With his team, he has now discovered a small RNA that comprises around 19 nucleotides and that regulates tuber formation depending on temperature. If temperatures rise, it blocks the formation of SP6A and thus the formation of tubers.

In the second phase, the scientists created potato plants in which the effect of the small RNA was deactivated and exposed the plants to high temperatures in the greenhouse. The result was that these plants continued to produce good quality tubers even at temperatures of over 29 degrees during the day or 27 degrees at night. “Our results offer us the means of still being able to grow potatoes in future at increasing temperatures,” says Prof. Dr. Sonnewald. The next step for the researchers is testing the potato plants under field conditions to see whether they can withstand high temperatures in realistic conditions.