Soy plants produce a quarter more beans if their sun protection system is genetically altered. This is apparent from field trials by American researchers. Their results are this Thursday in science published. They expect that their invention will eventually lead to higher crop yields, especially in Sub-Saharan Africa and South Asia, where production is too low to feed their own rapidly growing population.
Plants need sunlight to, in combination with CO2 and water, to make sugars and to store energy. But when there is too much sunlight, the extra energy is used to convert oxygen into oxygen radicals, which are harmful to the process of photosynthesis, among other things.
“With too much sunlight, all kinds of things can go wrong in a plant,” says Herbert van Amerongen, professor of biophysics at Wageningen University & Research, and not involved in the research that has now been published. Plants protect themselves against too much sunlight by switching on a system that “does not convert the surplus of incoming energy into electrons, but dissipates it in the form of heat,” says Van Amerongen, who is researching this system.
The disadvantage of this protection system is that although it switches on within seconds to minutes if there is too much sunlight, it switches off much more slowly when that abundance has passed. While the system is still active, photosynthesis does not run at maximum capacity.
tobacco plants
“Our idea was that a plant can grow faster if the protection system is turned off more quickly,” explains Steven Long. He coordinated the study and is a professor of crop science at the University of Illinois. Long proved the principle earlier with genetically engineered tobacco plants in which the protective system on three parts (two enzymes, and part of the photosynthesis apparatus) had been changed. As a result, the above-ground part of the tobacco plants increased in weight by 14 to 21 percent. The results are in 2016 in science published.
But subsequent experiments with genetically engineered thale cress showed no weight gain. The researchers then tested whether they could possibly improve the yield of an important agricultural crop by using the same procedure. They chose soy.
Their tests show that in 2020 the soybean harvest, measured by weight, increased on average 24.5 percent. They tested five different soy varieties, one of which gave a 33 percent higher yield.
severe storm
But in 2021, the harvest was lower, and it was comparable to that of the non-engineered soy varieties. Although the researchers counted an average of 13 percent more pods on the manipulated soy plants, the weight of beans was no higher. They explain that due to a violent storm just as the soybean plants were starting to make beans (the pods had already been planted by then). As a result, the lower leaves were more covered by the upper leaves, and were in almost permanent shade. So they didn’t benefit from the genetic engineering. In addition, according to the researchers, the clouds in 2021 were less varied than in 2020, and with it the changes between sun and shade.
Van Amerongen finds an increase in the harvest of almost a quarter “quite a lot”. He says he was surprised by it. Also because the experiments with tobacco and thale cress showed such different results. “Tobacco is an easy plant. A lot of people didn’t believe it would work in soy.” According to Van Amerongen, it is great that the researchers have now shown that the intervention also works in an important agricultural crop. “But we still don’t know how it works.”
Long’s research received funding from the Bill & Melinda Gates Foundation, among others. Long: “The condition is that any technology we develop, including this one, must be available to farmers in poor countries duty-free.”