A microbe offers a natural solution against rice pathogens

Japanese researchers have identified a favourable bacterium that could be used as a biocontrol agent in rice crops as an alternative to chemical pesticides

by Matteo Cavallito

 

Analysis of the interactions between certain microbes would open the way for environmentally sustainable solutions in the control of rice pathogens. This is the conclusion of a study published in the journal Environmental Microbiology Reports. The investigation, which involved a team of researchers led by Professor Yuuki Furuyama of the Department of Applied Biological Sciences at Tokyo University of Science (TUS), focused on the relationship between microorganisms: Pyricularia oryzae, a filamentous ascomycete fungus, and Streptomyces griseus, a bacterium capable of benefiting the soil.

Blast of rice

Rice is a staple food for more than half the world’s population. Its cultivation, then, is crucial to food security, notes a statement from Tokyo University. Pyricularia oryzae, which is responsible for a disease known as blast of rice. This poses a significant threat to crops and is typically dealt with chemical fungicides, which, however, can have a harmful environmental impact and contribute to the development of resistant strains.

For this reason, the note continues, researchers are exploring alternative strategies that exploit natural microbial interactions to promote plant health and manage disease in a more sustainable way.

“While extensive research has been conducted on how rice blast fungi infect their host rice plants, many aspects of their life cycle remain poorly understood,” explains Dr. Furuyama. “Our study aims to shed light on the interactions between rice blast fungi and other microorganisms in the soil, exploring the crucial part of their life cycle beyond the infection process.”

The research

To study these interactions, the researchers measured pH changes in a culture medium and observed the effects on the growth of Streptomyces griseus under different conditions. According to the authors, the presence of Pyricularia oryzae significantly increased the pH of the culture medium and favoured the growth of the bacterium despite the absence of direct contact between the two microorganisms. According to the study, the compound responsible for the pH increase could be the polyamine produced by the fungus.

The discovery appears truly remarkable. Indeed, Streptomyces is capable of producing antibiotics that can suppress the growth of pathogens such as Pyricularia oryzae.

By promoting the spread of the bacterium, in other words, the harmful fungus would thus inadvertently create the conditions to control its own spread. “P. oryzae and S. griseus may share a common niche, possibly in rice plants, and maintain a competitive relationship. S. griseus have potential as a new biocontrol agent for P. oryzae with minimal environmental impacts,” the study explains.

A nature-based solution

According to the researchers, the findings may have wider implications for understanding the impact of pH modulation on microbial interactions. This, they explain, could pave the way for the development of innovative, natural strategies for managing other plant diseases. Making less use of harmful chemical agents in the future.

“Our findings suggest that S. griseus could be used as a biocontrol agent in rice fields, offering an alternative to chemical fungicides,” says Dr. Furuyama. “If we can enhance the growth of S. griseus in rice paddies, we may be able to reduce the impact of rice blast in an environmentally friendly way”.