RESUMO
The action of metabolites and exoenzymes from rhizobacteria on different plant-parasitic nematodes has an influence on the nematicidal efficacy of the microbe. Seven rhizobacteria, divided into two bacterial groups, were evaluated in vitro for nematicidal activity on Meloidogyne ethiopica and Xiphinema index. The direct effect of their filtrates on egg hatching and juveniles of M. ethiopica as well as mobile stages of X. index was evaluated during a 72-h period. The production of four exoenzymes and two metabolites associated with nematode mortality was investigated. Molecular characterization of three isolates was performed, and the physiological profiles and lipase activity of all isolates were obtained using the BIOLOG EcoPlate system. While chitinase and collagenase were measured using the BIOLOG MT2 plate system, protease, hydrogen cyanide and hydrogen sulphide were directly determined in Petri dishes. Nematode mobile stages exposure to the bacterial filtrate revealed a nematicidal effect up to 93.7% on X. Index and up to 83.3% on M. ethiopica. The control of egg hatching varied between 35 and 85%. A positive correlation was found between the mortality of both nematode mobile stages and the concerted activities of the bacterial enzymes as well as the level of the volatile metabolites. The nematicidal effect of rhizobacteria strains varies by nematode genera and among the developmental stages evaluated.
Assuntos
Antinematódeos/farmacologia , Nematoides/crescimento & desenvolvimento , Rhizobiaceae/fisiologia , Solanum lycopersicum/parasitologia , Animais , Proteínas de Bactérias/farmacologia , Quitinases/farmacologia , Colagenases/farmacologia , Cianeto de Hidrogênio/farmacologia , Sulfeto de Hidrogênio/farmacologia , Nematoides/classificação , Nematoides/efeitos dos fármacos , Filogenia , Rhizobiaceae/classificação , Rhizobiaceae/enzimologia , Especificidade da EspécieRESUMO
AIMS: To identify enzymes and metabolites in the rhizobacteria filtrates that have a nematicidal effect on Xiphinema index and perform molecular characterization of the strains evaluated. METHODS AND RESULTS: A series of four bacteria selected for their nematicidal potential were considered for in vitro, biochemical and molecular studies. The direct effect of the bacterial filtrates was evaluated in vitro on X. index juveniles and adults. Hydrogen sulphide and hydrogen cyanide liberation and protease, chitinase, collagenase and lipase activity were verified in the strains. Up to five housekeeping genes and one ITS 16S-23S rRNA were analysed. All bacterial filtrates presented 54-100% mortality when evaluated during up to 72 h of nematode exposure. Strains presented protease activity; two of them (strains FB833T and FR203A) showed reliable collagenase and chitinase activities, respectively, and three of them showed strong lipolytic activity (FB833T, FR203A and FS213P). Strain Bacillus megaterium FB133M had no lipase activity and presented the lowest nematicidal effect. Bacillus amyloliquefaciens FR203A had the largest lethal effect. CONCLUSION: The rhizobacteria strains evaluated in this study possess nematicidal compounds, which may offer an interesting alternative for X. index control. SIGNIFICANCE AND IMPACT OF THE STUDY: This is the first report of exoenzymes and metabolites associated with nematicidal effect of rhizobacteria on X. index, which can be a possible alternative for control of this plant-parasitic nematode.
Assuntos
Antinematódeos/farmacologia , Proteínas de Bactérias/farmacologia , Nematoides/efeitos dos fármacos , Rhizobiaceae/química , Rhizobiaceae/enzimologia , Animais , Antinematódeos/metabolismo , Proteínas de Bactérias/metabolismo , Quitinases/metabolismo , Quitinases/farmacologia , Endopeptidases/metabolismo , Endopeptidases/farmacologia , Feminino , Masculino , Nematoides/crescimento & desenvolvimento , Rhizobiaceae/metabolismoRESUMO
An extensive survey was performed from 2002 to 2006 to detect and identify phytoplasmas associated with Chilean grapevines. Nested polymerase chain reaction assays using phytoplasma universal primer pairs P1/P7 and R16F2n/R2 detected phytoplasmas in 34 out of the 94 samples tested (36%). Restriction fragment length polymorphism (RFLP) analyses, cloning, and sequencing allowed identification of phytoplasmas belonging to ribosomal subgroups 16SrI-B, 16SrI-C, 16SrVII-A, and 16SrXII-A. The 16SrVII-A phytoplasma represents a new finding in grapevine; moreover, variability of the RFLP profile was observed in some of the 16SrXII-A phytoplasmas, indicating possible new ribosomal subgroups. Mixed phytoplasma infections and infections of phytoplasmas together with one or more viruses also occurred.