First Report of Pestalotiopsis clavispora and Pestalotiopsis spp. Causing Postharvest Stem End Rot of Avocado in Chile

Avocado (Persea americana) production in Chile has increased to more than 33,500 ha. Chilean avocadoes are sent to markets 15 to 45 days away by overseas transport to the United States, Europe, and Asia. Although apparently healthy avocadoes were harvested in 2009, a 10 to 14% incidence of stem end rot appeared after 15 days of cold storage. Symptoms appeared as small, irregular, brown lesions on the peel at the stem end. Lesions enlarged rapidly, became sunken and soft, eventually comprising the entire fruit as ripening progressed. A white mycelium often developed around the stem cavity. A dark brown necrosis of the pulp was observed that comprised a big part of the pulp as the fruits matured. Isolations were performed from 'Hass' avocadoes that developed stem end rot after fruits were kept in humid chambers for 15 days at 5°C plus 6 days at 20°C (n = 50) to simulate a transport period from Chile to U.S. markets or from diseased fruits (n = 50) kept for 15 days at 20°C. Fruits were surface disinfected for 60 s in 75% ethanol, and small pieces of tissue were excised from the margins of the pulp lesions and then plated onto potato dextrose agar (PDA) plus 1 ml/liter of Igepal CO-630 (Sigma-Aldrich, Atlanta, GA) (MPDA). Fungal colonies that developed on PDA were white and cottony, turning slightly yellow after 15 days. Black acervuli appeared after 15 days at 20°C. Conidia (n = 40) were fusiform, (22.2) 27.0 to 30.4 × (6.3) 7.0 to 9.8 μm with a length/width ratio of 3.4 ± 0.4. All isolates had five-celled conidia. Apical and basal cells were colorless, while the three median cells were dark brown. Conidia had one basal appendage (9.3 ± 3.3 μm) and two to four long apical appendages (34.5 ± 6.9 μm). On the basis of colony and conidia morphology, most of these isolates were initially identified as Pestalotiopsis clavispora (G.F. Atk) Steyaert, but other nonidentified species of Pestalotiopsis were also found (3). Identification was confirmed by amplifying and sequencing the internal transcribed spacer (ITS) region of rDNA using ITS1/ITS4 primers of P. clavispora isolate PALUC-12 (Accession No. HQ659767). A BLAST search of the NCBI database showed that isolate PALUC-12 had 100% homology with P. clavispora (No. EU342214.1). Pathogenicity tests were conducted on surface-disinfected (75% ethanol, 30 s) fruits by placing agar pieces (3 mm in diameter) from 7-day-old cultures and a 20-μl drop of 10⁶ conidia/ml on wounded and unwounded stem cavities and equatorial area of five avocado fruits of 'Hass', per isolate tested, at the commercial maturity stage. Inoculated fruits were placed in moist chambers at 25°C for 10 days. Necrotic lesions resembling symptoms that occurred in storage fruits were observed on wounded fruits. No symptoms were observed on unwounded fruits inoculated in the equatorial zone. However, unwounded fruits inoculated in the stem cavity developed a slight necrosis probably because of undetectable wounds made at harvest. Koch's postulates were confirmed after the reisolation of P. clavispora and Pestalotiopsis spp. from diseased fruits. P. versicolor has been reported in South Africa (1), but to our knowledge, this is the first report of P. clavispora causing stem end rot of avocado. P. clavispora has been reported on blueberry in Chile (2). References: (1) J. M. Darvas and J. M. Kotzé. Phytophylactica 19:83, 1987. (2) J. G. Espinoza et al. Plant Dis. 92:1407, 2008. (3) E. F. Guba. Monograph of Pestalotia and Monochaetia. Harvard University Press, Cambridge, MA, 1961.

Application of biofilm reactors to improve ammonia oxidation in low nitrogen loaded wastewater

An airlift reactor using zeolite particles as carrier material was used for the nitrification of effluents from the aquaculture industry. During the start-up the nitrogen concentration was kept around 100 mg NH4(+)-N/L to develop the nitrifying population. Later it was decreased down to around 3 mg NH4(+)-N/L and the dilution rate was increased up to 4.8 d(-1) in order to simulate the conditions in a an aquaculture waster treatment system. A nitrogen loading rate (NLR) of 535 mg NH(+)-N/m2 d was fully oxidized to nitrate. Higher values of NLRs caused nitrite accumulation. A second biofilm reactor was fed with a synthetic medium containing 50 mg NH4(+)-N/L which simulated the effluents from anaerobic units treating domestic wastewater. A nitrogen loading rate of 400 mg NH4(+)-N/L d was oxidized into nitrate with an efficiency of 60% at a dilution rate of 8 d(-1). Both biofilm systems allowed the development of a nitrifying population to treat the studied types of wastewaters.

Functional changes induced by psychological stress are not enough to cause intestinal inflammation in Sprague-Dawley rats

BACKGROUND

It is well known that stress contributes to the perpetuation of several gastrointestinal diseases. However, its role as a trigger of the inflammatory process in absence of other putative contributing factors remains controversial. Our aim was to elucidate whether stress per se can induce a primary gut inflammation in non-predisposed rats.

METHODS

Male Sprague-Dawley rats were divided in sham and stress groups. Chronic stress was induced by subjecting animals 1 h day(-1) to wrap restraint or water avoidance stress alternatively for five consecutive days, as a model of ongoing life stress.

KEY RESULTS

Chronic stress induced a significant decrease in body weight gain without changes in food intake and an increase in frequency of defecation. Electromiografic (EMG) study showed that the duration of the migrating motor cycles (MMCs), but not its frequency, was shortened in stressed animals compared with non-stress conditions. Moreover, stressful stimulus caused mucosal mast cell hyperplasia and a decrease of iNOS mRNA expression. Bacterial translocation observed in stressed animals was not related to changes in epithelial barrier function and was not enough to induce intestinal inflammation.

CONCLUSIONS & INFERENCES

Decreased MMC duration, mast cell hyperplasia and decreased mRNA iNOS expression, but not altered epithelial barrier function, could be factors implicated in bacterial translocation-induced by chronic stress. However, these changes are not sufficient to induce intestinal inflammation in stress non-susceptible strain of rats.

High harmonic emission from a superposition of multiple unrelated frequency fields

We report observations and analysis of high harmonic generation driven by a superposition of fields at 1290 nm and 780 nm. These fields are not commensurate in frequency and the superposition leads to an increase in the yield of the mid-plateau harmonics of more than two orders of magnitude compared to using the 1290 nm field alone. Significant extension of the cut-off photon energy is seen even by adding only a small amount of the 780 nm field. These observations are explained by calculations performed in the strong field approximation. Most importantly we find that enhancement is found to arise as a consequence of both increased ionization in the sum-field and modification of the electron trajectories leading to an earlier return time. The enhanced yield even when using modest intensity fields of 5 x 10(13) Wcm(-2) is extended to the 80 eV range and is a promising route to provide a greater photon number for applications in XUV imaging and time-resolved experiments at a high repetition rate.

Population dynamics of Epicoccum nigrum, a biocontrol agent against brown rot in stone fruit

AIMS

To study the population dynamics of Epicoccum nigrum on peaches and nectarines and to enhance its colonization on fruit surfaces to improve its biocontrol efficacy against brown rot.

METHODS AND RESULTS

Twelve surveys were performed to study E. nigrum populations and their effect on the number of the pathogenic Monilinia spp. conidia in peach orchards in Spain and Italy between 2002 and 2005. Fresh conidia and five different formulations of E. nigrum conidia were applied three to six times to peach and nectarine trees from full flowering to harvest. The size of the E. nigrum populations was determined from the number of colony-forming units and conidial numbers per flower or fruit. Treatment with all conidial formulations increased the size of the indigenous conidial population on peach surfaces.

CONCLUSIONS

Formulations of E. nigrum having high viability are most effective against conidia of the pathogen when applied at pit hardening and during the month immediately before fruit harvest.

SIGNIFICANCE AND IMPACT OF THE STUDY

Application of an E. nigrum conidial formulation decreased the number of conidia of Monilinia spp. on fruit surfaces during the growing season to the same extent as fungicides.

Nanofabrication with pulsed lasers

An overview of pulsed laser-assisted methods for nanofabrication, which are currently developed in our Institute (LP3), is presented. The methods compass a variety of possibilities for material nanostructuring offered by laser-matter interactions and imply either the nanostructuring of the laser-illuminated surface itself, as in cases of direct laser ablation or laser plasma-assisted treatment of semiconductors to form light-absorbing and light-emitting nano-architectures, as well as periodic nanoarrays, or laser-assisted production of nanoclusters and their controlled growth in gaseous or liquid medium to form nanostructured films or colloidal nanoparticles. Nanomaterials synthesized by laser-assisted methods have a variety of unique properties, not reproducible by any other route, and are of importance for photovoltaics, optoelectronics, biological sensing, imaging and therapeutics.

Extension of high harmonic spectroscopy in molecules by a 1300 nm laser field

The emerging techniques of molecular spectroscopy by high order harmonic generation have hitherto been conducted only with Ti:Sapphire lasers which are restricted to molecules with high ionization potentials. In order to gain information on the molecular structure, a broad enough range of harmonics is required. This implies using high laser intensities which would saturate the ionization of most molecular systems of interest, e.g. organic molecules. Using a laser at 1300 nm, we are able to extend the technique to molecules with relatively low ionization potentials (approximately 11 eV), observing wide harmonic spectra reaching up to 60 eV. This energy range improves spatial resolution of the high harmonic spectroscopy to the point where interference minima in harmonic spectra of N(2)O and C(2)H(2) can be observed.

Mucosal mast cells mediate motor response induced by chronic oral exposure to ovalbumin in the rat gastrointestinal tract

We previously demonstrated that oral chronic exposure to ovalbumin (OVA) causes intestinal hypermotility in Sprague-Dawley rats. In this study, the objective was to determine the mechanism of action of OVA and the role of mucosal mast cells in the regulation of motor activity in this model. Rats were orally exposed to OVA during 6 weeks. Intestinal mucosal mast cells (IMMCs) were counted and rat mast cell protease II (RMCPII) measured in duodenum, jejunum, ileum and colon. Anti-OVA IgE, IgG, and IL-4 were measured in serum. Eosinophils and IgE(+) cells were counted in jejunum. In an additional study rats were treated with the mast cell stabilizer ketotifen and mast cell number, RMCPII concentration and motor activity in vitro were evaluated. OVA exposed rats showed an increase in mucosal mast cell number and in RMCPII content in small intestine and colon. However, variables of a Th(2) type response were not affected by exposure to OVA: (i) neither OVA specific IgE nor IgG were found; (ii) IL-4 did not increase and, (iii) the number of eosinophils and IgE(+) cells was identical in the exposed and unexposed groups. These results brought us to hypothesize a possible non-Ig-mediated action of OVA on mast cells. Ketotifen significantly diminished the response to OVA: Ketotifen reduced the number of mast cells and the RMCPII content and blocked increased intestinal contractility. In addition ketotifen modified motor response in both OVA exposed and unexposed animals giving evidence of the importance of mast cells in intestine motor activity driving.

Hyperalgesia, synovitis and multiple biomarkers of inflammation are suppressed by interleukin 1 inhibition in a novel animal model of gouty arthritis

BACKGROUND

Monosodium urate (MSU) and calcium pyrophosphate dihydrate (CPPD) crystal-induced interleukin 1 beta (IL1beta) release contributes to inflammation in subcutaneous air pouch and peritoneal models of acute gout and pseudogout. However, consequences of IL1 inhibition have not been explored in more clinically relevant models of crystal-induced arthritis.

OBJECTIVE

To develop a novel mouse model of acute gouty ankle arthritis and use it to assess the effects of genetic deletion of IL1 receptor type (IL1R1) and of exogenous mIL1 Trap (a high-affinity blocker of mouse IL1alpha and IL1beta) on pain, synovitis and systemic inflammatory biomarkers.

METHODS

MSU crystals were injected into the mouse ankle joint and pain and ankle swelling were measured over 4 days. The effects of IL1 inhibition were determined in this model, and in the comparator models of crystal-induced peritonitis and subcutaneous air pouch inflammation.

RESULTS

Both IL1R1-null mice and mice pretreated with mIL1 Trap showed reduced neutrophil influx in MSU and CPPD crystal-induced peritonitis and air pouch models (p<0.05). In the ankle joint model, both IL1R1 knockout mice and pretreatment with mIL1 Trap were associated with significant reductions in MSU crystal-induced elevations in hyperalgesia, inflammation, serum amyloid A and the levels of multiple inflammatory cytokines and chemokines (p<0.05). Additionally, it was found that administration of mIL1 Trap after MSU crystal injection reduced established hyperalgesia and ankle swelling.

CONCLUSIONS

IL1 inhibition both prevented and relieved pain and ankle joint inflammation in response to intra-articular MSU crystals in mice. Results suggested that IL1 Trap has the potential to both prevent and treat gouty arthritis.

Characterization of nitrogen-doped carbon nanotubes by atomic force microscopy, X-ray photoelectron spectroscopy and X-ray absorption near edge spectroscopy

In this work, we perform a comparative study on single-walled carbon nanotubes (CNT) before and after low energy nitrogen ion bombardment (70 eV and 25 x 10-6 A/cm2) at room temperature. The morphology and the mechanical properties were studied by Atomic Force Microscopy (AFM). The bonding configuration of the N-doped CNTs was established by X-ray Photoelectron Spectroscopy (XPS) and X-ray Absorption Near Edge Spectroscopy (XANES). Single-walled carbon nanotubes were prepared using non-intrusive methods and deposited onto silicon substrates. For the spectroscopic studies, samples with a high concentration of CNTs were analyzed. XPS reveals different chemical states for carbon related to the incorporation of nitrogen. XANES confirms the hexagonal structure of the CNTs, resembling the bonding structure of hexagonal carbon nitrides. AFM images confirm that the CNTs were not destroyed after low energy N2+. The morphology of the original nanotubes maintains after nitrogen ion bombardment except for the incorporation of some pearl-shaped decoration, probably due to the adsorption of some contaminants or to deposition of re-sputtered material. Whereas CNTs improve their adherence to the substrate, this extra granularity on the CNT is easily removed even with the AFM tip. In conclusion, spectroscopic measurements and mechanical properties made clear information on the changes produced on CNT after nitrogen incorporation.

Injectable iron-modified apatitic bone cement intended for kyphoplasty: cytocompatibility study

In this study, the cytocompatibility of human ephitelial (HEp-2) cells cultured on new injectable iron-modified calcium phosphate cements (IM-CPCs) has been investigated in terms of cell adhesion, cell proliferation, and morphology. Quantitative MTT-assay and scanning electron microscopy (SEM) showed that cell adhesion and viability were not affected with culturing time by iron concentration in a dose-dependent manner. SEM-cell morphology showed that HEp-2 cells, seeded on IM-CPCs, were able to adhere, spread, and attain normal morphology. These results showed that the new injectable IM-CPCs have cytocompatible features of interest to the intended kyphophasty application, for the treatment of osteoporotic vertebral compression fractures.

Identification of Phytophthora cryptogea as the Cause of Rapid Decline of Petunia (Petunia × hybrida) in Chile

Phytophthora cryptogea was consistently isolated from diseased tissue taken from the crown and necrotic roots of grandiflora type petunia (Petunia × hybrida) that were collected in gardens in five public parks in Santiago, Chile in 2004 and 2005. Symptoms included leaf wilting and foliar chlorosis, followed by partial necrosis, and extensive dark-brown to reddish cankers in the crown. Disease incidence was over 50% and infected plants died within 7 to 10 days after transplanting. This pathogen was identified on the basis of colony morphology, morphological characterization of the sexual and asexual reproductive structures, and temperature range. The identification of Phytophthora cryptogea was further corroborated by the internal transcribed spacer sequence analysis (GenBank accession number EF093534). Isolates of P. cryptogea were pathogenic on 10-week-old white grandiflora petunia plants that were inoculated on the roots or on the crown using mycelium fragments, or via soil inoculation using zoospores. A rapid decline was observed after soil inoculations with zoospores. Root fresh weight decreased significantly and the root rot index and severity of foliage symptoms increased significantly (P ≤ 0.05), relative to noninoculated plants after 14 days of incubation. Two isolates (Ph-1 and Ph-2) were pathogenic on bell pepper and one isolate (Ph-1) was pathogenic on tomato after root inoculation. Two isolates (Ph-2 and Ph-3) were pathogenic on the fruit of avocado, bell pepper, cherry tomato, cucumber, kiwifruit, lemon, pear, pepino, and potato tubers, demonstrating the pathogen's ability to cause postharvest infection of fruit of a wide range of host plants. The efficacy of mefenoxam at 0.1 mg/ml mixed with either chlorothalonil at 1.0 mg/ml or mancozeb at 1.6 mg/ml was demonstrated in this study, whereas chlorothalonil and mancozeb alone did not control disease development. No significant differences were obtained between foliage and soil drench applications. This study demonstrated that P. cryptogea is the cause of the rapid decline found on petunia in Santiago, Chile and, to our knowledge, this is the first report giving a detailed description of a disease caused by P. cryptogea on petunia.