Compatibility of Azospirillum brasilense with Pesticides Used for Treatment of Maize Seeds

Abstract

<jats:p>Seed treatment with chemical pesticides is commonly used as an initial plant protection procedure against pests and diseases. However, the use of such chemicals may impair the survival and performance of beneficial microorganisms introduced via inoculants, such as the plant growth-promoting bacterium <jats:italic>Azospirillum brasilense</jats:italic>. We assessed the compatibility between the most common pesticide used in Brazil for the treatment of maize seeds, composed of two fungicides, and one insecticide, with the commercial strains Ab-V5 and Ab-V6 of <jats:italic>A. brasilense</jats:italic>, and evaluated the impacts on initial plant development. The toxicity of the pesticide to <jats:italic>A. brasilense</jats:italic> was confirmed, with an increase in cell mortality after only 24 hours of exposure <jats:italic>in vitro</jats:italic>. Seed germination and seedling growth were not affected neither by the <jats:italic>A. brasilense</jats:italic> nor by the pesticide. However, under greenhouse conditions, the pesticide affected root volume and dry weight and root-hair incidence, but the toxicity was alleviated by the inoculation with <jats:italic>A. brasilense</jats:italic> for the root volume and root-hair incidence parameters. In maize seeds inoculated with <jats:italic>A. brasilense</jats:italic>, the pesticide negatively affected the number of branches, root-hair incidence, and root-hair length. Therefore, new inoculant formulations with cell protectors and the development of compatible pesticides should be searched to guarantee the benefits of inoculation with plant growth-promoting bacteria.</jats:p>

Impact of seed-applied fungicide and insecticide on Azospirillum brasilense survival and wheat growth-promoting ability

“…There are few reports related to the effect of pesticides on Azospirillum spp. While some pesticides such as benomyl, thiamethoxam and tebuconazole seemed to be compatible with A. brasilense (Pereyra et al 2009;Elslahi et al 2014;Munareto et al 2018) pyraclostrobin + thiophanate-methyl, were not (Munareto et al 2018;Vogel and Fey 2019;Pereira et al 2020;Santos et al 2020aSantos et al , 2020b. The compatibility depends on the tested pesticide, the sensitivity of the biological inoculant and the applied inoculation methodology.…”

The Challenge of Combining High Yields with Environmentally Friendly Bioproducts: A Review on the Compatibility of Pesticides with Microbial Inoculants

“…However, regular colonies were recovered after the bacteria were grown under optimal conditions, indicating an adaptive mechanism to the stressful conditions when exposed to the pesticides. Santos et al [26] evaluated the compatibility of Standak ® Top with A. brasilense strains Ab-V5 and Ab-V6. First, differences were observed between strains, with lower tolerance of Ab-V5, so that after 24 h of exposure the recovery of viable cells dropped from 4.56 × 10 5 to 4.37 × 10 2 cells seed −1 .…”

Growth, respiratory activity and chlorpyrifos biodegradation in cultures of Azotobacter vinelandii ATCC 12837

“…The evaluation of the effects of the most widely used OP worldwide on PGPR has gained interest because tolerant organisms could maintain their promoting activities, establish in contaminated sites, even used as potential decontaminating agents (Sumbul et al 2020 ; Chitara et al 2021 ). Tolerance and degradation to various pesticides by PGPR have been evaluated in the genera Azospirillum (Santos et al 2020 ), Bacillus (Praveen Kumar et al 2014 ), Klebsiella (Rani et al 2019 ), Pseudomonas (Giri and Rai 2012 ), Serriata (Cycón et al 2013 ) , Ochrobactrum (Abraham and Silambarasan 2016 ) and Azotobacter (Chennappa et al 2018a , b ), the latter being one of the most important for agricultural proposes.…”