Willian César Terra

Microbiota from Meloidogyne exiguaegg masses and evidence for the effect of volatiles on infective juvenile survival

Egg masses of Meloidogyne exiguafrom coffee plants are subjected to a range of microbial populations and these resident soil organisms in the egg masses may affect nematode communities. The incidence of fungi and bacteria in M. exiguaegg masses was investigated and the toxic effect of their volatile organic compounds (VOCs) was tested on second-stage juveniles (J2). Bacteria and fungi were isolated from egg masses on coffee root and identified to species. The nematicidal activity of VOCs from bacterial and fungal strains was tested against M. exiguain in vitroexperiments. Several bacterial and fungal strains were found in M. exiguaegg masses and produced VOCs that were toxic to M. exiguaJ2. Bacterial strains induced more nematode mortality compared with fungal strains. The continued colonisation of fungi and bacteria in M. exiguaegg masses occurred during the year and their VOCs reduced the viable inocula of M. exiguaand should be explored as biocontrol agents.

Volatile compounds produced by Fusarium spp. isolated from Meloidogyne paranaensis egg masses and corticous root tissues from coffee crops are toxic to Meloidogyne incognita

Meloidogyne species produce egg masses containing nutrients which may serve as feeding substrate for rhizospheric fungi. In the present work we isolated fungi form Meloidogyne paranaensis egg masses. Amongst the fungi isolated 67% belonged to the genus Fusarium and, within those, 52% of the isolates were of the species F. oxysporum. Isolates from F. oxysporum and F. solani significantly reduced M. incognita infectivity and reproduction in tomato when J2 were exposed to fungal volatiles, causing up to 100% immobility in in vitro tests. Water exposed to the volatile compounds produced by fungi and mixed to the J2 suspension caused toxicity in M. incognita J2 and reduced infectivity and reproduction of nematodes inoculated in tomato, when compared to the control. Using gas chromatography-mass spectrometry (GC-MS), the volatile compounds produced by F. oxysporum and F. solani were identified and gathered in six main categories: esters, alcohols, phenols, aldehydes, carboxylic acids and sesquiterpenes, making up a total of 23 molecules. For the first time, 12 molecules from various chemical groups were identified in the water exposed to the volatiles from F. oxysporum and F. solani. A lower number of molecules were detected in the toxic water when compared with the vapors produced by fungi. Within these molecules, various have been already reported as having high nematicidal activity. Thus, F. oxysporum and F. solani fungi from M. paranaensis egg masses produce volatile compounds with antagonistic activity to M. incognita.

ESTIRIL-LACTONAS DE Cryptocarya aschersoniana Mez. (Lauraceae Juss.) COM ATIVIDADE CONTRA Meloidogyne spp. E INTERAÇÃO IN SILICO COM PROVÁVEL FUMARASE DEMeloidogyne hapla

In a previous study, substances with nematicidal properties were detected in the bark of Cryptocarya aschersoniana. Continuing such study, the methanol extract from this plant underwent fractionation guided by in vitro assays with the plant-parasitic nematode Meloidogyne exigua. Two active compounds were isolated and identified by spectroscopic methods as (E)-6-styrylpyran-2-one and (R)-goniothalamin. The latter compound was also active againstMeloidogyne incognita. In silico studies carried out with (R)-goniothalamin and the enzyme fumarate hydratase, which was extracted from the genome of Meloidogyne hapla and modeled using computational methods, suggested that this substance acts against nematodes by binding to a cavity close to the active site of the enzyme.