Root and shoot development of corn seedlings as affected by multifunctional microorganisms

Abstract

Corn is the most produced cereal in the world, due to its high production and, mainly, its wide use (OLIVEIRA, 2019). The crop is one of the most important agricultural commodities worldwide, and it is the main energy source for animal feed, in the cuisine of several countries, and an important source in the production of renewable fuel (CONAB, 2019). The world's largest producers are the United States, China and Brazil, which produce approximately 392, 257 and 82 million tons, respectively (FAO, 2021).

Corn is an important product in the Brazilian agriculture, and it is produced practically throughout the country, as an important source of income and with good participation in the national economy (MIRANDA, 2018). The current production model most used for this crop is based on excessive applications of pesticides and synthetic fertilizers, generating severe problems for the environment and also financial impacts. These damages caused by the intensive use of synthetic fertilizers, herbicides, fungicides and insecticides show the need to seek alternatives that provide the sustainable development of agriculture (LOPES; ALBUQUERQUE, 2018). According to Silva et al. (2020), among the existing alternatives to increase the efficiency of the use of chemical fertilizers and reduce the amount applied in agricultural production environments, the use of microorganisms that promote plant growth can be highlighted.

Among the microorganisms selected in the rhizosphere, plant growth-promoting rhizobacteria (PGPR) stand out, which have a high affinity for occupying the rhizospheric environment and are capable of performing activities related to promoting plant development (CARDOSO; ANDREOTE, 2016). This plant growth promotion is linked to the ability of this group of microorganisms to act positively on physiological growth characteristics, using different mechanisms of action, such as nutrient solubilization, inhibition of pest and plant pathogen development, production of bactericides, antifungals, growth hormones, siderophores and biological nitrogen fixation (LAKSHMANAN et al., 2015). Several plant growth-promoting rhizobacteria have been frequently isolated from the rhizosphere of several cultivated plants and have been studied, such as: Agrobacterium, Arthrobacter, Bacillus, Burkholderia, Pseudomonas, Serratia, Azotobacter, Staphylococcus e Azospirillum (MAHMOOD et al., 2016).

In this context, the use of multifunctional microorganisms represents a biotechnology option whose objective is to promote plant growth by promoting greater development of the root system, increasing nutrient absorption, gas exchange efficiency and, consequently, phytomass production and grain yield (NASCENTE et al., 2017). The greater root development promoted by multifunctional microorganisms can also promote, in addition to greater use of nutrients, easier access to water (GLICK, 2012). Several studies report greater plant development with the use of multifunctional microorganisms and cite the production of hormones as one of the possible causes for this greater development in rice cultivation (SPERANDIO et al., 2017; SOUSA; NASCENTE; FILIPPI, 2019; FERNANDES et al., 2021), wheat (SPAEPEN et al., 2008) and corn (RAZA; FAISAL, 2013; NAVEED et al., 2015), demonstrating the potential use of this biotechnology in the Poaceae family.

Studies done by researchers of Embrapa Rice and Bean allowed the identification of beneficial rhizobacteria collected in upland rice fields (FILIPPI et al., 2011). After selection and characterization, greenhouse studies confirmed the potential use of these multifunctional microorganisms, which promoted significant increases in gas exchange and in the production of aboveground biomass of upland and irrigated rice plants (NASCENTE et al., 2017). Therefore, it became interesting to carry out studies to evaluate the use of these isolates in different cultures of great importance, as has already been done in upland rice, irrigated rice, common beans and soybeans (this included the work of the staff). Thus, it is also possible that these microorganisms positively affect the development of corn plants. The objective of this work was to determine the effect of seed inoculation with multifunctional microorganisms on root and shoots development of corn seedlings.