Ultrasensitive immunoassay for detection of Citrus tristeza virus in citrus sample using disposable microfluidic electrochemical device.

Tristeza is a disease that affects citrus crops in general, caused by the Citrus tristeza virus (CTV). It is considered an economically important virus diseases in citrus, which is present in the main citrus producing regions all around the world. Early detection of CTV is crucial to avoid any epidemics and substantial economic losses for the citrus growers. Consequently, the development of rapid, accurate, and sensitive methods capable of detecting the virus in the early stages of the disease is highly desired. Based on that, a low-cost and rapid magneto-immunoassay methodology to detect the capsid protein from CTV (CP-CTV) was proposed. For this, magnetic beads were decorated with antibodies anti-CP-CTV and horseradish peroxidase enzyme (HRP) and applied for the capture and separation of CP-CTV from the sample solutions. The magnetically captured biomarker was detected using a simple disposable microfluidic electrochemical device (DµFED) constructed by rapid prototyping technique and composed by an array of immunosensors. In DµFED, the electrodes were modified with monoclonal antibody anti-CP-CTV and the detection was carried out using amperometry, based on the hydroquinone/H2O2 catalytic redox reaction due to the presence of HRP label in an immune-sandwich structure. The proposed immunoassay presented excellent linearity with a wide linear range of concentration of 1.95-10.0 × 103 fg mL-1 and ultralow detection limit of 0.3 fg mL-1. The disposable device was successfully applied for the detection of Citrus tristeza virus in healthy and infected plant samples, where it showed good agreements with the comparative method of enzyme-linked immunosorbent assay (ELISA). The developed immunoassay methodology showed a sensitive and selective way in the detection of CTV. Hence, it can be considered as a promising analytical alternative for rapid and low-cost diagnosis of Tristeza disease in citrus.

Laboratory and field evaluation of acetic acid-based lures for male Asian citrus psyllid, Diaphorina citri.

The Asian citrus psyllid (ACP) is a vector of a pathogen associated with greening and thus a major problem in citriculture worldwide. Lures are much needed for improving ACP trapping systems for monitoring populations and surveillance. Previously, we have identified acetic acid as a putative sex pheromone and measured formic acid- and propionic acid-elicited robust electroantennographic responses. We have now thoroughly examined in indoor behavioral assays (4-way olfactometer) and field tests the feasibility of these three semiochemicals as potential lures for trapping ACP. Formic acid, acetic acid, and propionic acid at appropriate doses are male-specific attractants and suitable lures for ACP traps, but they do not act synergistically. An acetic acid-based homemade lure, prepared by impregnating the attractant in a polymer, was active for a day. A newly developed slow-release formulation had equal performance but lasted longer, thus leading to an important improvement in ACP trap capture at low population densities.

Putative sex pheromone of the Asian citrus psyllid, Diaphorina citri, breaks down into an attractant.

Under laboratory conditions, mating activity in Asian citrus psyllid (ACP) started 4 days after emergence, peaked at day 7, and showed a clear window of activity starting 8 h into the photophase and extending through the first hour of the scotophase. We confirmed that ACP males are attracted to emanations from conspecific females. Traps loaded with a candidate compound enriched with female extract, lignoceryl acetate (24Ac), at various doses were active only after being deployed for several weeks in the field, suggesting that a degradation product, not the test compound, was the active ingredient(s). Lignocerol, a possible product of 24Ac degradation, was not active, whereas acetic acid, another possible degradation product, was found in the airborne volatile collections from lures matured under field conditions and detected in higher amounts in volatiles collected from females at the peak of mating activity than in male samples. Acetic acid elicited dose-dependent electroantennographic responses and attracted ACP males, but not females, in Y-type and 4-way olfactometers. Field tests showed that acetic acid-baited traps captured significantly more males than control traps. Surprisingly, captures of females in acetic acid-baited traps were also higher than in control traps, possibly because of physical stimuli emitted by captured males.

Analysis of alternariol and alternariol monomethyl ether on flavedo and albedo tissues of tangerines (Citrus reticulata) with symptoms of alternaria brown spot.

A method was developed for the quantification of alternariol and alternariol monomethyl ether on tangerines with and without symptoms of Alternaria brown spot disease. The method employs solid-phase extraction for cleanup, followed by high-performance liquid chromatography coupled with tandem mass spectrometry (HPLC-MS/MS) for detection. This method was validated on flavedo (exocarp or epicarp, exterior yellow peel) and on albedo tissue (mesocarp, interior white peel). An excellent linearity over a range of 0.50-20.0 mg/kg was achieved, with r2 >or= 0.997. The limits of detection (LOD) and quantification (LOQ) were fewer than 0.13 and 0.50 microg/kg, respectively. The relative standard deviations (RSDs) were

Efficacy of essential oil of Piper aduncum against nymphs and adults of Diaphorina citri.

BACKGROUND: Insecticide application is the main way to control Diaphorina citri. However, it causes environmental contamination, has a negative impact on beneficial organisms and leads to psyllid resistance. The essential oil of Piper aduncum has low toxicity towards the environment and contains dillapiol, which has proven to be effective against several crop pests. Here, we studied its efficacy against nymphs and adults of D. citri under laboratory conditions. Oils with three concentrations of dillapiol (69.3, 79.9 and 85.4%) at 0.5, 0.75 and 1.0% dilutions plus 0.025% adjuvant were tested. RESULTS: All treatments caused 90-100% mortality in nymphs. Topical treatments with oil containing 79.9 and 85.4% dillapiol at 0.75% and 1% dilutions were effective (mortality ≥80%) in adults. However, the essential oil showed no residual activity against adults (mortality ≤30%). CONCLUSIONS: Dillapiol-rich oil is a promising compound for D. citri control. © 2015 Society of Chemical Industry.

Three highly oxygenated caryophyllene sesquiterpenes from Pestalotiopsis sp., a fungus isolated from bark of Pinus taeda.

A Pestalotiopis sp. was isolated from the trunk bark of Pinus taeda. The fungus was cultivated in liquid medium and produced three highly oxygenated caryophyllene sequiterpene derivatives, named pestalotiopsolide A, taedolidol and 6-epitaedolidol, respectively. The sesquiterpenes were isolated by silica gel based chromatographic procedures and their structures were elucidated by NMR spectroscopic data.