Abstract
Avoiding the toxicity effect of chemical fungicides on rhizobacteria is a sustainable alternative for agroecosystem management. Rhizobacteria, whose bioprotective and plant growth-promoter potential have been reported in the literature, lack studies on their performance in integrated management with pesticides. Thus, this study aimed to evaluate the effects of azoxystrobin + cyproconazole on the growth of Bacillus subtilis, Streptomyces seoulensis, and Bradyrhizobium japonicum. Three independent experiments were set up, i.e., one for each microorganism, and carried out in a completely randomized design in a factorial scheme (3 × 6), with three doses (recommended by the manufacturer, half, and twice) and six periods of evaluations (48, 96, 144, 192, 240, and 288 hours), with three replications. Growth inhibition rings were evaluated. Azoxystrobin + cyproconazole at all tested doses is compatible with B. subtilis. The use of azoxystrobin + cyproconazole affected the growth of B. japonicum and S. seoulensis, which were sensitive to all its doses until 288 hours after inoculation.
Highlights
Plant growth-promoting (PGP) microorganisms are organisms that colonize the rhizosphere and rhizoplane and improve plant growth when artificially inoculated into seeds or soil
The first factor consisted of three doses of the fungicide Priori Xtra, i.e., the dose recommended by the manufacturer (300 mL commercial product ha−1 for soybean), half, and twice the recommended dose, while the second factor consisted of six evaluation periods (48, 96, 144, 192, 240, and 288 hours after inoculation), with three replications
B. subtilis Bs10 had no sensitivity to the in vitro in azoxystrobin + cyproconazole for the three tested doses, as inhibition rings were not formed over the evaluated hours
Summary
Plant growth-promoting (PGP) microorganisms are organisms that colonize the rhizosphere and rhizoplane and improve plant growth when artificially inoculated into seeds or soil. PGP microorganisms can promote plant growth by direct stimulation, such as iron chelation, phosphate solubilization, nitrogen fixation, and phytohormone production (Hao et al, 2011; Panhwar et al, 2012), or indirect stimulation, such as plant pathogen suppression and induction of resistance in host plants against pathogens (Qiao et al, 2014; Sousa and Olivares, 2016). Related to plant interactions can be divided into biofertilization, biostimulation, and bioprotection (Saharan and Nehra, 2011). All these microorganisms can be used in agriculture to promote plant growth or control agricultural diseases and pests. For this to be possible, these microorganisms must not be affected by other practices carried out in current agriculture, such as the use of chemicals such as fungicides
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