A special study, from University of California - Berkeley, have demonstrated that fertilizer destroys plant microbiome ability to protect against disease. But both natural microbiomes and synthetic biomes constructed from normal populations are protective against pathogens. If successfully used in practice, the findings strongly suggest a role for targeting the root microbiome as a novel potential treatment for general health of the plant than fertilizer. According to the researchers.
The study have been published in the journal Current Biology.
Fertilizing crops may make them more susceptible to disease
University of California, Berkeley, biologists found that spraying tomatoes with microbes from healthy tomatoes protected them from disease-causing bacteria, but that fertilizing the tomatoes beforehand negated the protection, leading to an increase in the population of pathogenic microbes on the plants' leaves.
While the researchers don't yet know whether the increased number of bad bacteria on the leaves actually makes the tomatoes sick, the study clearly shows that fertilizer throws the community of microbes on the leaves off-balance. That potentially could allow disease-causing organisms to enter the plant.
"When we change the nutrient environment that plants are in, we are fundamentally altering the plant-microbiome interaction and also, importantly, the microbiome-mediated protection of natural plant/microbe interactions," said senior author Britt Koskella, a UC Berkeley assistant professor of integrative biology.
Sometimes low doses of microbiomes work better than high doses
The fertilizer effect was not the only surprise from the study, Koskella said. She and co-author Maureen Berg, a graduate student, were investigating how the density of the microbial community on the leaves affected the plants' resistance to disease and discovered that a lower dose of beneficial microbes sprayed on the leaves was often more effective in protecting the plants from infection than higher doses. Berg sprayed leaves with an artificial microbial community composed of 12 species of bacteria taken from the natural microbiome of healthy tomatoes.
"We found that the most protective community was the most dilute, the least concentrated, the lowest dose," she said. "This was completely nonintuitive. A medium dose gave medium protection and the highest dose was the least protective."
The reasons are unclear, but the findings are important because organic farmers are talking about spraying crops with probiotics to encourage better growth and disease protection, in the same way that humans consume probiotics containing "good" microbes in hopes of improving their health.
Original title：Fertilizer destroys plant microbiome's ability to protect against disease