Plant growth promoting microorganisms help crops to resist drought

Researchers warn of increasingly frequent extreme weather events in the future as a result of climate change. In addition to storms and floods, these will include long periods of drought. Such dry periods, which often last for weeks and have been occurring more frequently both on inland areas and on the coasts of Central Europe, are becoming a serious problem for agricultural production. Many intensively cultivated crops around the world show little tolerance of prolonged drought, leading to substantial yield losses in the future. At the same time, the growing world population is increasing the yield pressure on the available agricultural land.

Researchers from the Institute for General Microbiology (IfAM) at Kiel University have now examined the current state of plant research in a comprehensive meta-analysis of numerous publications from recent years to determine particularly promising approaches to combat plant drought stress. Overall, the comparison of different growth parameters showed that the introduction of bacterial symbionts has a significantly stronger growth-promoting effect under drought conditions than fungi. The research team recently published the results in the scientific journal Physiologia Plantarum.

Endophytic bacteria and fungi protect crops against
drought

In principle, there are various ways to influence the plant response to water shortage, such as the targeted modification of certain genes responsible for drought tolerance. An important, technologically less complex and environmentally friendly approach is the use of certain plant growth promoting endophytic microorganisms: Endophytic fungi and bacteria, i.e. microorganisms that colonize the inside of a plant, are introduced into crops in a process known as inoculation. Seeds, leaves or roots can be treated by immersing them in a microorganism solution, for example. Once active in the host organism, these can help in various ways to adapt to dry growing conditions.

In recent years, numerous research papers have reported on the benefits of such endophytic microorganisms improving the drought resistance of crops. The Kiel scientists from Professor Ruth Schmitz-Streit's group on Molecular Biology of Microorganisms compared the plant growth-promoting effect of such bacteria and fungi on the basis of about 170 scientifically published experiments between 2010 and 2021 and identified the various processes by which they stimulate plant growth under drought stress.

"Based on the existing literature, we wanted to find out which processes determine the stress reduction and which method shows the greatest overall effectiveness“, said Dr Muhammad Aammar Tufail, first author of the study and postdoctoral researcher in Schmitz-Streit's working group. To do this, the researchers combined data from a large number of studies to summarize and balance the effects of inoculation with bacteria and fungi based on standardized growth parameters such as the increase in biomass, the measurement of leaf surface or chlorophyll content. “From our global observation, we can deduce that the effect of inoculation with endophytic bacteria is at least twice as large based on our growth criteria and that they can experimentally mitigate drought stress in agricultural plants significantly and more efficiently than fungi", Tufail continues.

Potential applications in agriculture

"Our comprehensive meta-analysis sheds light on important conceptual foundations for further research into microorganisms as plant inoculants in sustainable agriculture", emphasises IfAM-director Schmitz-Streit, who is active in Kiel University’spriority research area Kiel Marine Science (KMS). "In this way, we are making an important contribution to analysing and further developing the promising approaches based on bacterial inoculation in terms of their effectiveness. Further research must clarify whether such experimental effects on plant growth can also be transferred to practical applications in agriculture in order to produce more drought-tolerant crops in regions of the world that are particularly threatened by climate change in the future", Schmitz-Streit summarises.

Dr. Muhammad Aammar Tufail
Molecular Biology of Microorganisms
Institute of General Microbiology (IfAM)
Kiel University
mtufail@ifam.uni-kiel.de
+49/431/880-4337

Prof. Dr. Ruth Schmitz-Streit
Molecular Biology of Microorganisms
Institute of General Microbiology (IfAM)
Kiel University
rschmitz@ifam.uni-kiel.de
+49/431/880-4334