The results of studies about interactions between microorganisms involving at least one plant pathogen are of interest to the areas of ethiology and control in Plant Pathology. Various aspects of these interactions have been studied over the years but the toxicity of volatile organic compounds (VOCs) has been emphasized only recently, developing techniques and procedures, and producing additional knowledge to those already obtained with water-soluble substances. This new facet of these interactions based on VOCs is discussed in this review involving mainly fungi, bacteria and nematodes pathogenic to plants. Also discussed is the role of VOCs produced by microorganisms, especially fungi and bacteria, in soil fungistasis and the effect of VOCs on fungal agents used in the control of plant parasitic nematodes. The evidence of VOCs broadens the research studies about these interactions. However, the scarcity of the research results in this area show up gaps which need to be filled and some research proposals are discussed. The present and future accumulated VOC knowledge will perhaps be beneficial to farmers, especially aspects related to increasing soil suppressiveness to plant disease and to the finding of analog molecules of VOCs highly effective against plant pathogens.Index terms: Biological control, volatiles, plant pathogens, interaction. RESUMOOs resultados dos estudos sobre interações entre microorganismos quando envolve, no mínimo, um patógeno de plantas são de interesse às áreas de etiologia e controle de fitodoenças. Vários aspectos dessas interações têm sido, por muitos anos, estudados, porém, a toxicidade de compostos orgânicos voláteis (COV) tem sido enfatizada apenas recentemente, desenvolvendo-se técnicas e rotinas, além de produzir conhecimentos adicionais àqueles já obtidos por meio de pesquisas com substâncias solúveis em água. Essa nova faceta dessas interações, envolvendo COVs, é discutida nesta revisão, enfatizando, principalmente, o antagonismo a fungos, bactérias e nematóides patogênicos de plantas. Também é discutido o papel dos COVs produzidos por microorganismos especialmente, fungos e bactérias envolvidos na fungistase do solo, bem como o efeito dos COVs nos agentes fúngicos usados no controle de fitonematóides. A evidência comprovada dos COVs nessas interações amplia esse campo de pesquisa. Entretanto, a escassez de pesquisas nessa área afloram lacunas no conhecimento científico que precisam ser preenchidas e, desta forma, algumas propostas de pesquisas são discutidas. O conhecimento científico presentemente acumulado nessa área de pesquisa, juntamente com aquele a ser produzido, serão, talvez, úteis aos produtores rurais, especialmente nos aspectos envolvendo a constatação de supressividade de solo a fitodoenças e aos testes com moléculas análogas dos COVs altamente tóxicos a patógenos de plantas.Termos para indexação: controle biológico, voláteis, patógenos de plantas, interações.

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Castor bean cake incorporated into the soil produces volatile compounds which are toxic to M. incognita. These substances show potential for application in the nematicide-producing industry. © 2018 Society of Chemical Industry.

The second stage juvenile (J2) of Meloidogyne spp. spend the storaged energy of the body, differently, when living in variable conditions of soil temperatures and humidities approaching to the incapability of plant parasitism. Therefore, the aim of this work was to study the storage of J2 of M. incognita in soil at d i f f e r e n t l e v e l s o f h u m i d i t y a n d t e m p e r a t u r e , b e s i d e s w a t e r bubbling of inoculum suspension on the infectivity of starved J2 in tomato. The infectivity of J2 in tomato decreased significantly among storaged temperatures during the period of six days in soil. Greatest (P<0,01) infectivity occurred when J2 was storaged at 8

Ethanol (EtOH) is less harmful to humans than currently available nematicide molecules. This study evaluated the efficacy of EtOH in controlling Meloidogyne incognita in vitro and in lettuce plants under glasshouse conditions. Aqueous EtOH solutions (5-70% volume) and their vapours caused an acute nematicidal effect in vitro in second-stage juveniles (J2) of M. incognita and reduced hatching of J2. There was a large reduction of galls and eggs in the root system when 40 ml of EtOH was applied to M. incognita-infested soil at concentrations of 40 and 70%. Water exposed to EtOH vapours for 1 h became toxic, and a 12-h exposure caused 100% J2 mortality. Use of a plastic cover did not increase the efficiency of EtOH in controlling M. incognita in lettuce plants. The observed EtOH effects indicate its prospective use in controlling plant-parasitic nematodes, especially in glasshouses.

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Despite the great benefits arising from the adoption of Roundup Ready® (RR®) soybean, there are reports about the lack of selectivity of glyphosate for this crop. The use of growth-promoting microorganisms can help attenuate the injuries caused by herbicides. The objective of this work was to evaluate the agronomic performance of RR® soybean submitted to the post-emergence application of glyphosate both isolated and in association with Bacillus subtilis. The experiment was carried out in a completely randomized block design, with four replications. The treatments consisted of the post-emergence applications of glyphosate (1296 g a.i. ha−1), glyphosate (2592 g a.i. ha−1), glyphosate/glyphosate (1296/1296 g a.i. ha−1), glyphosate + B. subtilis BV02 (1296 + 42 g a.i. ha−1), glyphosate + B. subtilis BV02 (2592 + 42 g a.i. ha−1), and glyphosate + B. subtilis BV02/glyphosate + B. subtilis BV02 (1296 + 42/1296 + 42 g a.i. ha−1). The application of glyphosate (2592 g a.i. ha−1) and the sequential application of glyphosate provides higher levels of intoxication. The association of B. subtilis BV02 with glyphosate (2592 g a.i. ha−1) prevented losses in the values of relative chlorophyll a and b and the total chlorophyll index. The soybean yield was reduced when the plants were submitted to a sequential application of glyphosate.

Crop yield decrease is the main concern when a pathogen or plague is identified in an agriculture field. Thus, part of this issue can be attributed to plant-parasitic nematodes (PPNs), such as Meloidogyne species, due to, most of the time, the hard diagnosis, and non-specific symptoms. Its management is mainly based on chemical pesticides, followed by a few potential biological control agents, and the management system. Therefore, this study aimed to evaluate the effects of biological agents in Meloidogyne incognita control in different soil systems. For that, two biological products were chosen, Trichoderma asperellum BV10 and Bacillus amyloliquefaciens BV03, and soils were sampled from three different managements systems: (i) soybean no-tilled system at Goi&aacute;s state, Brazil; (ii) forest soil at Goi&aacute;s state, Brazil, and (iii) soybean conventional managed system at Mato Grosso do Sul state, Brazil. Biocontrol and growth promotion effects, volatile organic compounds (VOCs) and soil respiration were determined in vegetation house and laboratory, respectively. As a result, both BV10 and BV03 had significant nematode control activity, comparing to control treatment, in all the three soils systems. Plus, the number of immobile nematodes by potential VOCs had significant increase when BV03 was applied, while the application of BV10 agent raised the soil respiration rate. In conclusion, both biocontrol agents presented great efficiency in control M. incognita, with better performance of BV03. Lastly, more studies must be done to elucidate how the resident soil microbiome can influence on biocontrol agent establishment and performance, as well as the consequence of the application of biological products on soil microbiome network.