The chemicals that farmers spray on their crops in form of pesticides to kill pests and prevent diseases have always been a bone of contention, with researchers trying to find safer alternatives. A new variety of rice that fights multiple pathogens with no effect on the yield of the crop, is thus a welcome relief for both farmers and scientists.
The discovery is based on a study of the plant’s immune system. Plants use receptors on the outside of their cells to identify molecules that signal a microbial invasion, and respond by releasing antimicrobial compounds. Therefore, identifying genes that kickstart this immune response yields disease-resistant plants.
Just like sick humans who are unproductive at work, plants grow poorly and produce unfavourable yields when their immune systems are overloaded. For a long time, scientists have focused on the NPR1 gene from a small, woody plant called Arabidopsis thaliana, to boost the immune systems of rice, wheat, tomatoes and apples.
However, NPR1 is not very useful for agriculture because it has negative effects on plants. To make it useful, researchers needed a better gene that would activate the immune response only when the plant is under attack. Rice with the gene was able to combat rice blast which often causes an estimated 30 per cent loss of rice crop worldwide, every year.
A segment of DNA called the TBF1 cassette acted as a control switch for the plant’s immune response. When the TBF1 cassette from the Arabidopsis genome was copied and pasted alongside and in front of the NPR1 gene in rice plants, it resulted in a strain of rice that could fend off offending pathogens without causing stunted growth seen in previously engineered crops.
The researchers tested the superiority of engineered rice over regular rice by inoculating crop leaves with the bacterial pathogens that cause rice blight and leaf streak, as well as the fungus responsible for blast disease. Whereas the infections spread on the leaves of wild rice plants, the engineered plants confined the invaders to a small area.
The researchers say this innovation could come in handy in the developing world where farmers with no access to fungicide often lose their entire crop to disease. The study was published in Nature.