Sun-smart rice varieties more productive

Australian scientists have improved rice productivity by selecting rice varieties that are better at capturing sunlight to produce grains, instead of reflecting it as heat.

Rice is the most important crop for global food security. It is currently a staple source of food for four billion people worldwide, and this number is increasing rapidly, making the improvement of rice yields an urgent focus for plant scientists.

In a study published in Plant Physiology, a team of scientists focused on rice’s natural diversity by using traditional breeding techniques to select cultivated varieties — or cultivars — that are better at converting sunlight into food.

“We studied hundreds of plants from five rice cultivars and found that there is variation between these varieties in relation to the quantity of light they use for growth or dissipate as heat. Some of them are capable of converting more sunlight into chemical energy, producing greater leaf area over time,” said lead researcher Dr Katherine Meacham, from the ARC Centre of Excellence for Translational Photosynthesis.

When leaves intercept sunlight, this sunlight is either absorbed by the leaf and converted via the process of photosynthesis into the plants own components (leaves, grains, roots, etc); dissipated as heat as a strategy to protect the proteins of the plant from sun damage (photoprotection); or re-emitted as fluorescent light. In this study, the researchers measured fluorescence to infer the quantity of energy that is either converted into food or dissipated as heat.

“Recently, scientists in the US found that they can produce transgenic plants that are better at catching sunlight without getting sun damage. Our work shows that this is also achievable by taking advantage of the natural variation of rice plants,” said Professor Robert Furbank, director of the ARC Centre of Excellence for Translational Photosynthesis and one of the authors of the study.

“We found that there is room for improvement in some cultivars that can result in more photosynthesis, without risking the plant’s protection strategies against sunlight damage,” said Dr Meacham.

Traditional breeding for photosynthetic traits has not been a common strategy in any major cereal crop, in part due to the difficulty in measuring photosynthesis in thousands of plants. However, rapid screening tools are now available to study the interaction between the genes and the way they interact with the environment.