At the University of Massachusetts Amherst, scientists recently found that the ability of agricultural grasses to sustain drought conditions is directly associated with the health of the microbial community surviving on their leaves, stems and seeds.
Microbes do an enormous amount for the grasses that drive the world’s agriculture. They protect from pathogens, provide the grass with nutrients such as nitrogen, supply hormones to bolster the plant’s health and growth, protect from UV radiation and help the grass manage drought.
Emily Bechtold, Study Lead Author and Graduate Student, Department of Microbiology, University of Massachusetts Amherst
The study was published in Applied and Environmental Microbiology and reveals that the increased longevity and severity of climate-change-induced drought conditions across the globe tend to weaken the ability of the microbiome to survive.
About 60% of all agriculture is related to grass — considering sheep, cows and other grass-munching livestock that offer milk, meat, cheese, wool, leather and other staples. Therefore, the bacteria living on grass have an impact on every aspect of human life, ranging from food security, economics to international development.
In first-of-its-kind research, scientists concentrated on two types of grasses. One prevails majorly in grasslands in temperate zones and the other one predominant in tropical regions.
The goal of this research is to be able to manage the interactions between plants and the bacteria they host in order to support a truly sustainable agriculture.
Klaus Nüsslein, Study Senior Author and Professor of Microbiology, University of Massachusetts Amherst
So far, there was no detail regarding the way grass and its microbiome supported one another and on how the bacterial community is affected by drought.
The researchers were supported by the Lotta M. Crabtree Foundation and the National Science Foundation to grow their temperate and tropical grasses in two different greenhouses. The climate of each greenhouse was maintained to simulate natural climatic conditions.
As soon as the grasses were mature, the team further segregated each group into three different sub-groups. The first one was the control group maintained at optimum conditions, the second was maintained under a climate mimicking mild drought and the third one experienced severe drought conditions.
Throughout a month, the researchers counted, collected and sequenced the DNA of the bacteria from all the grass groups and compared the results.
They observed that when the bacteria exhibited signs of drought-induced stress, the plants reflected the same. In line with the expectation, the tropical grasses were better at sustaining drought compared to the temperate grasses.
However, remarkable variations were found in the microbiomes of all grasses subjected to severe drought conditions. Apart from the existence of fewer total bacteria, the microbial community became less diverse and thus resilient to environmental stress. In certain cases, an increase in the count of bacteria detrimental to grass was observed.
Yet, there was some ray of hope. A few potentially beneficial bacteria were found to survive under mild drought conditions. According to Bechtold, more research is required on this front.
The research shows that plans are required to actively support and biofertilize these beneficial bacteria to overcome the drought conditions, which could become more widespread in the era of global warming.
Bechtold, E. K., et al. (2021) Phyllosphere Community Assembly and Response to Drought Stress on Common Tropical and Temperate Forage Grasses. Applied and Environmental Microbiology. doi.org/10.1128/AEM.00895-21.