Modern agriculture faces challenges that are constantly multiplying and renewing in the perspective of achieving higher crop yields, and that these have the least possible impact on the environment.

This task is resorting to new approaches and integrating ecological and molecular concepts to achieve these higher yields and incidentally reduce the impacts on the environment to a minimum, significantly reducing the doses of synthetic fertilizers, which cause pollution, damage to human health. and loss of soil fertility.

Rhizobacteria

In this work, the search has been directed towards the development of new biotechnologies, with a growing interest in beneficial soil microorganisms that promote plant growth and prevent infections of plant tissue by pathogens.

Specifically, a promising method to reduce the use of synthetic fertilizers is the application of plant growth promoting rhizobacteria (RPCV), as microbial inoculants, because the use of RPCV as biofertilizers is a viable and sustainable option that facilitates the availability of elements nutritious, promotes growth and increases the productive yields of plants.

What are CPRs

All the Plant growth-promoting rhizobacteria (PGPR, for its acronym in English), or RPCV, correspond to a set of bacteria that inhabit the rhizosphere (root environment) of plants and that produces all kinds of benefits in them, such as enhancing their growth, improving the absorption of minerals and other types of compounds, protect them from possible pathogens, combat soil contamination and help them in the production of hormones necessary for their development.

These characteristics mean that PGPRs are currently highly investigated, not only for their collaboration in the growth of crops, or as biocontrol agents, but also for their multiple possibilities of soil decontamination and ecosystem recovery. At present, even genetically modified bacterial strains are being investigated, which improve and enhance this interaction under conditions that were previously unfavorable.

Action and interaction

The action of inoculating crops with RPCV, in addition to reducing the use of synthetic fertilizers and their consequent negative impacts, increases crop yield, contributing to economic profitability for producers and incidentally, to the health of the population.

These interactions of RPCV with plants and microorganisms (biotic environment) are very complex and use various mechanisms of action to influence plant growth, such as biofertilization, phytostimulation or biocontrol.

From the root

An essential factor for RPCV to efficiently actuate this biological control and favor plant growth is the colonization of their root system. In this regard, the essential elements for this colonization to be efficient include the ability of microorganisms to survive after inoculation and grow in the spermosphere (region that surrounds the seed), it must also be fixed on the surface of the first roots and colonize the whole system.

This root colonization by endophytic microorganisms (within the plant) includes several stages, such as attraction, recognition, adhesion and invasion, which are affected by the living and non-living physical and chemical components of the ecosystem (biotic and abiotic factors). The colonization of the seeds is the first step in this process, because the microorganisms that settle on the seeds can grow and colonize the roots to their full extent.

Good results in cultures depend on an adequate colonization of bacteria in the rhizosphere. Applying the correct inoculation technique, this will be reflected in a higher percentage of germination and productivity of the crop, in addition to increasing its resistance to stress.

PGP and RPCV

RPCVs are located within the framework of plant growth promotion mechanisms, or Plant Growth Promotion (PGP), which are those actions or biological activities that result in a positive influence on the development of the plant, and can be classified into direct or indirect mechanisms, or a combination of both.

Direct and indirect

Direct mechanisms occur when bacteria synthesize metabolites, or when plants increase the availability of nutritional elements necessary for their metabolism, improving their nutrition, nitrogen fixation (N), the synthesis of phytohormones, vitamins and enzymes, the solubilization of phosphorus. (P) inorganic and organic phosphate mineralization, or the reduction of toxicity by heavy metals, the reduction of ethylene levels in the soils, or the increase of the permeability of the roots, among others.

In the case of indirect mechanisms, these are based on aspects of the metabolism or biology of the microorganism, so they should not necessarily exert a positive effect on the development of the plant, however they collaborate, because the RPCV cause the decrease or elimination of phytopathogenic microorganisms, either through the production of antimicrobial substances or antibiotics, lytic enzymes or a combination of these. As well as by stimulating the natural defenses of the plant, through mechanisms of biocontrol and induction of systemic resistance (IRS) to a wide spectrum of pathogenic organisms and production of siderophores, among others, as well as the production of antibiotics and hydrogen cyanides that impact on phytopathogens.

More efficiency, better quality

These mechanisms allow optimizing resources, improving the efficiency of the crop in the use of edaphic (soil) resources, in addition to contributing to the health of the plant and its ability to respond to adverse conditions. This is especially relevant in the current climate change scenario and specifically in blueberries, which we know is a crop highly dependent on environmental conditions.

In addition, these microorganisms have the ability to increase the special qualities of blueberry, further concentrating the bioactive compounds that characterize it and for which consumers demand it in the markets.