Abstract
More than one hundred years have passed since the development of the first microbial inoculant for plants. Nowadays, the use of microbial inoculants in agriculture is spread worldwide for different crops and carrying different microorganisms. In the last decades, impressive progress has been achieved in the production, commercialization and use of inoculants. Nowadays, farmers are more receptive to the use of inoculants mainly because high-quality products and multi-purpose elite strains are available at the market, improving yields at low cost in comparison to chemical fertilizers. In the context of a more sustainable agriculture, microbial inoculants also help to mitigate environmental impacts caused by agrochemicals. Challenges rely on the production of microbial inoculants for a broader range of crops, and the expansion of the inoculated area worldwide, in addition to the search for innovative microbial solutions in areas subjected to increasing episodes of environmental stresses. In this review, we explore the world market for inoculants, showing which bacteria are prominent as inoculants in different countries, and we discuss the main research strategies that might contribute to improve the use of microbial inoculants in agriculture.
Highlights
Humanity has always been concerned about food production to attend the increasing population and, for a long time, the solution was to expand agriculture to new areas
The most antique microorganisms used as inoculants are the “rhizobia”, diazotrophic bacteria able to colonize the rhizosphere and establish nodules in the roots of their host plants, composed by several species of the Fabaceae family
Santos et al AMB Expr (2019) 9:205 can fully supply the plants demands on N. Other diazotrophic bacteria, such as Azospirillum, establish less straight relationships with the host plant, but are able to supply, at least partially, the plant’s demands on N. Both Azospirillum and rhizobia, among other diazotrophic and non-diazotrophic bacteria are named as plant-growth-promoting bacteria (PGPB) or plant-growth-promoting rhizobacteria (PGPR), as they may benefit the plants by a variety of single or combined processes, including the production of phytohormones, siderophores, phosphate solubilization, induction of plant intrinsic systemic resistance to abiotic and biotic stresses, among others (Bhattacharyya and Jha 2012; Malusá and Vassilev 2014; Fukami et al 2017, 2018a, b)
Summary
Humanity has always been concerned about food production to attend the increasing population and, for a long time, the solution was to expand agriculture to new areas. In Brazil, co-inoculation of A. brasilense with Bradyrhizobium spp. for the soybean crop and with Rhizobium tropici for the common beans was launched in 2014 and impressive increases in grain yield have been reported (Hungria et al 2013, 2015; Souza and Ferreira 2017; Nogueira et al 2018).
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