Compatibilidade de microrganismos em campo e in vitro na promoção de crescimento e no manejo de doenças em soja

Abstract

The use of beneficial microorganisms for plants has proven to be an environmentally sustainable and economically profitable alternative. However, the use of multiple microorganisms in sowing furrows and their application together with fungicides in spray mixtures in disease management are issues that have not been completely clarified in the literature. The objective of this research was to evaluate the possibility of combining different microorganisms in the soybean sowing furrow and mixing bacteria with fungicides in spray mixture to control diseases in soybeans. For this, three experiments were carried out. The first experiment was carried out in the field with different combinations of inoculation and coinoculation in a sowing furrow, using the following microorganisms Bradyrhizobium japonicum, Azospirillum brasilense, Pseudomonas fluorescens and Trichoderma asperelloides. The second experiment was carried out in the laboratory in order to evaluate in vitro survival of Bacillus subtilis and Pseudomonas fluorescens when exposed to different fungicides, simulating a spray solution, through the mixture of a bacteria and a formulated product. The third experiment was also conducted in the field, testing different foliar treatments to control anthracnose (Colletotrichum truncatum) involving applications of chemical products and the bacteria Bacillus subtilis and Pseudomonas fluorescens, and a mixture of both in spray mixture. In the first experiment, the variables evaluated were: number of nodules, dry mass of nodules, surface area of roots, volume and length of roots, grain productivity, mass of one thousand grains and percentage of soil cover. In the second experiment, the survival of bacteria was evaluated by counting colony-forming units. In the third experiment, the following were evaluated: percentage incidence of anthracnose on petioles, percentage of defoliation, grain productivity and mass of one thousand grains. Under the conditions tested, in which there was water restriction, the use of microorganisms in the sowing furrow did not generate productivity gains in relation to the uninoculated control. Different responses were found in the survival of B. subtilis and P. fluorescens according to the active ingredient used, and for B. subtilis there was a reduction in survival for the active ingredients mancozeb, difenoconazole, picoxystrobin + benzovindiflupyr and impirfluxam + tebuconazole, while for P. fluorescens there was a reduction in survival for all fungicides tested. However, biological management involving both bacteria had a statistically equal effect to chemical management in controlling anthracnose and in soybean crop productivity, with biological management with both being an option in disease control..