About half of the world's population eats rice as a staple diet. Rice farming requires a lot of water, and roughly 15% of rice is farmed in drought-prone areas, according to the German assistance organisation Welthungerhilfe. As a result of global warming, rice production is becoming increasingly difficult, resulting in smaller yields and more frequent food shortages. Plant pathogen-caused crop failures exacerbate the problem even more. Pesticides, which are mostly employed as a preventive measure in rice cultivation, are being utilised to combat this in conventional agriculture. To combat these environmentally hazardous substances, the only option is to breed resistant plants, which is only somewhat successful at the moment. If the plants have developed resistance to one pathogen as a result of a genetic mutation,
Pathogen resistance is conferred by bacteria.
As a result, an international research group led by Graz University of Technology's Institute of Environmental Biotechnology has been examining the microbiome of rice plant seeds for some time in order to identify links between plant health and the presence of specific microbes. The group has now made a significant breakthrough. They discovered a bacterium inside the seed that can lead to total resistance to a pathogen that is passed down from plant generation to plant generation. The findings, which were published in the scientific journal Nature Plants, lay an entirely new foundation for developing biological plant protection products and lowering damaging biotoxins produced by plant infections.
Rice's microbiome is a collection of microorganisms that live in:
One genotype of rice plants (cultivar Zhongzao 39) has developed resistance to the plant disease Burkholderia plantarii in conventional rice production in the Chinese province of Zhejiang. This disease causes crop failures and creates a biotoxin that can induce organ damage and tumours in humans and animals who are repeatedly exposed to it. "Until now, the intermittent resistance of rice plants to this virus could not be explained," explains Tomislav Cernava of Graz University of Technology's Institute of Environmental Biotechnology. Cernava has been investigating the microbiome of rice seeds from different cultivation regions in detail in collaboration with Zhejiang University (Hangzhou) and Nanjing Agricultural University in China, as well as the Japanese Hokkaido University in Sapporo, with the help of microbiome luminary and Institute head Gabriele Berg and his institute colleague Peter Kusstatscher.
Bacterial composition as a major determinant
The scientists discovered that disease-resistant plants' seeds have a different bacterial composition than disease-susceptible plants' seeds. In resistant seeds, the bacterium genus Sphingomonas was identified much more frequently. As a result, the researchers extracted bacteria from the seeds and identified Sphingomonas melonis as the disease-resistant culprit. This bacterium makes an organic acid called anthranilic acid, which suppresses the pathogen and renders it harmless. "When isolated Sphingomonas melonis is administered to non-resistant rice plants, it also works. They become resistant to the plant disease Burkholderia plantarii as a result of this "Tomislav Cernava explains. Furthermore, the bacterium develops itself in specific rice genotypes and is naturally transmitted down from one plant generation to the next. "This discovery has immense promise. We will be able to employ this method in the future to reduce pesticide use in agriculture while maintaining good crop yields "Cernava says.
