Researcher Zhang Ruifu, of the Innovation Team of Agricultural Microbial Resources of the Institute of Agricultural Resources and Regional Planning (IARRP) of the Chinese Academy of Agricultural Sciences (CAAS), was invited to write a review article to systematically summarize the rhizosphere microbes that enhance crop salt tolerance and the underlying mechanism, and to anticipate the prospects of microbial fertilizers to improve crop yields in saline-alkali land. The article - "Rhizosphere microbes enhance plant salt tolerance: toward crop production in saline soil" was published in the Computational and Structural Biotechnology Journal.

Saline-alkali land is an important part of reserve farmland in China, and improving crop yields in saline-alkali land through agricultural microbial technology is of great significance in ensuring national food security. According to Associate Researcher Liu Yunpeng, the major cropping cultivars are sensitive to salt stress, and the yield of cultivation in saline-alkali land is low. In order to effectively utilize nearly 500 million mu of saline-alkali farmland in China for food production, improving saline-alkali land and breeding salt-tolerant crop cultivars through engineering means are the main strategies at present.

Rhizosphere microbes can effectively promote stress resistance in plants. Some beneficial microbes in the rhizosphere can significantly promote the growth of crops under salt stress. They have the potential to be developped into special microbial fertilizers for increasing production in saline-alkali land, being both low-cost and environmentally friendly.

The paper reviews the reported microbial species that can enhance plant salt tolerance, and sumarized the advantages and disadvantages of each bacterial group in agricultural applications, and further reviews the mechanism of rhizosphere microbes to enhance plant salt tolerance, mainly that: 1) Microbes can assist plants in re-establishing ion and osmotic balance; 2) Microbes can reduce the cell damage caused by the stress response in plants; 3) Microbes can resume plant growth under salt stress conditions. The review advocate the application prospect of using agricultural microbial technology and microbial fertilizer products to improve crop yields in saline-alkali land.

Zhang’s research group has long focused on rhizosphere microorganisms and microbial fertilizers to promote crop root development, nutrient absorption, and stress tolerance from the aspects of microbial resource isolation, mechanism analysis, microbial fertilizer development, and agricultural applications.

Focusing on the increase of crop production in saline-alkali land, they have isolated more than 1,000 bacterial strains that are able to enhance the salt tolerance of different crops from the rhizosphere of coastal halophytes and various types of saline-alkali soil, and have identified the key metabolites of rhizosphere microbe that enhance salt tolerance of crops. They have also revealed the underlying mechanism of microbial metabolites regulating crop salt tolerance (Physiologia Plantarum, 2016, https://onlinelibrary.wiley.com/doi/10.1111/ppl.12441,MolecularPlant-MicrobeInteractions, 2017, http://apsjournals.apsnet.org/doi/10.1094/MPMI-02-17-0027-R ). They have developed a special microbial fertilizer product for increasing production in saline-alkali land (ZL201910300563.5, a strain of Bacillus megaterium that promotes the growth of crops resistant to salt and alkali and a special microbial fertilizer for saline-alkali land and its application ; ZL201910359879.1, a rhizosphere growth-promoting bacterium that enhances the salt tolerance of crops and a microbial fertilizer and its application) and carried out field experiments with the final salt concentration at 3‰, 4‰, and 5‰ in the Bohai Granary Base in Wudi, Shandong, for three consecutive years.  Wheat and corn under different salt concentrations achieved a yield increase of 17-27% (Journal of Nanjing Agricultural University, 020, 43:452-459). The developed special microbial fertilizer product for saline-alkali land production is promoted and applied in cooperation with Heze Kingenta Ecological Engineering Co., Ltd.

Paper link: https://doi.org/10.1016/j.csbj.2022.11.046