Beneficial Plant-Associated Microorganisms From Semiarid Regions and Seasonally Dry Environments: A Review

Abstract

Semiarid regions are apparently low biodiversity environments; however, these environments may host a phylogenetically diverse microbial community associated with plants. Their microbial inhabitants are often recruited to withstand stressful settings and improve plant growth under harsh conditions. Thus, plant-associated microorganisms isolated from semiarid and seasonally dry environments will be detailed in the present review, focusing on plant growth promotion potential and the microbial ability to alleviate plant abiotic stress. Initially, we explored the role of microbes from dry environments around the world, and then, we focused on seasonally dry Brazilian biomes, the Caatinga and the Cerrado. Cultivable bacteria from semiarid and seasonally dry environments have demonstrated great plant growth promotion traits such as plant hormone production, mobilization of insoluble nutrients, and mechanisms related to plant abiotic stress alleviation. Several of these isolates were able to improve plant growth under stressful conditions commonly present in typical semiarid regions, such as high salinity and drought. Additionally, we highlight the potential of plants highly adapted to seasonal climates from the Caatinga and Cerrado biomes as a suitable pool of microbial inoculants to maintain plant growth under abiotic stress conditions. In general, we point out the potential for the exploitation of new microbial inoculants from plants growing in dry environments to ensure a sustainable increase in agricultural productivity in a future climate change scenario.

Exploitation of Plant Growth Promoting Bacteria for Sustainable Agriculture: Hierarchical Approach to Link Laboratory and Field Experiments

“…However, this approach is limited since it does not take into account that in real conditions the PGPB efficiency depends not only on the individual traits analysed but also on their interaction with other factors, which can be associated with both plants and the environment. Therefore, to identify efficient PGPB, it is essential to evaluate as many variables as possible in greenhouse experiments, in order to simulate the real field conditions [ 66 , 67 , 68 , 69 ]. Moreover, considering that the environmental conditions have strong influence on the microbial communities associated with plants, having information about the place of origin of the tested strains can be helpful for field application [ 67 , 68 ].…”

“…Therefore, to identify efficient PGPB, it is essential to evaluate as many variables as possible in greenhouse experiments, in order to simulate the real field conditions [ 66 , 67 , 68 , 69 ]. Moreover, considering that the environmental conditions have strong influence on the microbial communities associated with plants, having information about the place of origin of the tested strains can be helpful for field application [ 67 , 68 ]. The use of throughput sequencing of nucleic acids for molecular characterization of PGPB under real field conditions might be an effective approach to select PGPB candidates [ 69 ].…”

“…This adaptation is the result of their genetic plasticity but is also due to the action of the microorganisms associated with them. Since these microorganisms have experienced the same adaptation as their host plants, they could represent an optimal source for the selection of PGPB usable to improve plant growth under real field conditions where they are frequently subjected to different abiotic stress conditions [ 67 , 70 ].…”

From Lab to Farm: Elucidating the Beneficial Roles of Photosynthetic Bacteria in Sustainable Agriculture

“…In general, several beneficial microbial traits (i.e., in vitro PGP traits), such as BNF, phosphate solubilization, 1-aminocyclopropane-1-carboxylic acid (ACC) deaminase activity and siderophore and phytohormone production, are assessed via laboratory screening assays to select elite PGPR for the development of microbial inoculants [142]. However, many reports have already indicated that the existence of these PGP microbial traits in vitro is not absolutely associated with plant growth promotion [143,144]. Taking PNSB as an example, PS3, YSC3 and BCRC16408 (ATCC 17001 T ) are three closely related R. palustris strains [45].…”

The Role of Plant-Associated Bacteria, Fungi, and Viruses in Drought Stress Mitigation

“…Semiarid environments, such as the caatinga biome, are characterized by uneven distribution of rain throughout the year ( Alvares et al, 2013 ). Recent research has revealed the potential of bacteria associated with caatinga native plants as inoculants for plant growth promotion under drought conditions ( Bonatelli et al, 2021 ). The adaptations of the bacteria in caatinga might involve tolerance to high temperatures, desiccation tolerance genes, pigment production for protection against UV radiation, production of thermostable enzymes, and production of intracellular osmolytes ( Kavamura et al, 2013 ).…”