This paper presents the geographical distribution, biology and life cycle, symptoms of damage, pathotypes, races or biotypes, survival and spread, economic importance, and management measures (chemical, cultural and biological control methods, and pest resistance) of the parasitic nematodes of coffee and cocoa, with particular emphasis on Meloidogyne spp. and Pratylenchus spp.

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Isozymes (esterase and malate dehydrogenase), SCAR and RAPD-PCR were studied in 15 populations of three races of Meloidogyne exigua collected in coffee-producing areas in Brazil, Bolivia and Costa Rica and one population from rubber tree plantations in Brazil. This study revealed four esterase phenotypes (E1, E2, E2a, E3) and three malate dehydrogenase phenotypes (N1, N1a, N2) for M. exigua populations. The most common multi-enzyme phenotype was E2N1. The enzymatic phenotypes do not separate M. exigua races. Sixteen populations of M. exigua were tested in Multiplex PCR using SCAR primers ex-D15F/R that allowed the identification of all M. exigua populations. Phylogenetic analyses showed high intraspecific polymorphism (25.9-59.6%) for all M. exigua studied. However, all populations clustered together with 100% bootstrap support, thereby demonstrating the consistency of species identification. In general, no correlation was found between enzymatic profile, race and genetic polymorphism of the studied populations.

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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.

No abstract

This work aimed to select potentially useful rhizobacteria for the control of Meloidogyne exigua, a widely disseminated root-knot nematode found in Brazilian coffee fields. Initially, crude metabolites produced in liquid medium by 69 isolated rhizobacteria strains (previously obtained from several plants collected in the south of Minas Gerais State, Brazil) were tested in vitro for lethality towards M. exigua second stage juveniles (J 2 ). Substances produced by strains of Bacillus cereus, B. megaterium, B. pumilus, B. thuringiensis, Enterobacter asburiae, E. cloacae and Paenibacillus macerans caused high mortality in J 2 . Subsequently, the ten most active crude metabolites were selected and assessed for nematicidal activity in a biotest with M. exiguainoculated coffee plants. Although strains of B. cereus, B. pumilus and P. macerans caused a significant reduction in the number of root galls and/ or nematode eggs per plant 90 days after treatment, the best results were obtained with the application of B. megaterium strain 54-06.

Volatile organic compounds (VOC) produced by green residues for the management of plant-parasitic nematodes are poorly studied for oilseed plants and some Brassica spp. To investigate the activity of VOC in vitro and as biofumigants, dry and aqueous macerates of broccoli (Brassica oleracea var. italica) shoots and sunflower (Helianthus annuus) seed were used against the root-knot nematode Meloidogyne incognita. VOC produced by sunflower seed caused higher mortality of M. incognita second-stage juveniles (J) than VOC produced by broccoli shoots but both plant species were equally effective in decreasing the infectivity and reproduction of this nematode. The number of galls and eggs produced by the nematode in tomato roots was reduced by 89 and 95%, respectively, on average, at the highest concentrations of broccoli and sunflower seed macerates tested as biofumigants. When nematodes were placed in water exposed to broccoli VOC, J immobility increased and the number of galls and eggs produced by the nematode in tomato roots decreased 80 and 96%, respectively. Water exposed to sunflower seed VOC had no effect on the viability of the nematode. Gas chromatography was used to identify five and six chemical groups in broccoli and in sunflower seed macerates, respectively, but only alcohols, sulfurated VOC, and terpenes were detected in the water exposed to these plant macerates. Sulfurated VOC from the water exposed to broccoli macerates were found to be involved in its activity against M. incognita. The purified VOC dimethyl disulfide (DMDS) and 3-pentanol were tested directly against J and showed a lethal concentration of 176 and 918 µg/ml (ppm), respectively, whereas dimethyl sulfide had no effect against M. incognita. Furthermore, DMDS and 3-pentanol retained in water killed J and reduced gall formation and the number of eggs of M. incognita on tomato roots. Both these plant species produced toxic VOC to M. incognita, whereas only VOC retained in water exposed to broccoli had activity against M. incognita.