Ochratoxin A Contamination of California Pistachios and Identification of Causal Agents.

Ochratoxin A (OTA) is a potent mycotoxin produced by Aspergillus and Penicillium spp., which contaminates many crops, including pistachios. Pistachios contaminated with OTA may be subjected to border rejections resulting in significant economic losses to the United States agricultural revenues. The current study examined prevalence of OTA in California-grown pistachios and identified its causal agents. OTA was detected in 20% of samples from 2018 to 2021 (n = 809), with 18% of samples exceeding the European Union regulatory limit of 5 µg/kg. Fungi potentially responsible for OTA contamination were isolated from leaves, nuts, and soil collected from 14 pistachio orchards across California. A total of 1,882 isolates of Aspergillus section Nigri and 85 isolates of section Circumdati were recovered. Within section Nigri, 216 (11.5%) isolates were identified as potential OTA producers using a boscalid-resistance assay. Phylogenetic analyses of partial gene sequences for ß-tubulin and calmodulin genes resolved section Circumdati into four species: A. ochraceus (33%), A. melleus (28%), A. bridgeri (21%), and A. westerdijkiae (19%). A. westerdijkiae produced the highest levels of OTA in inoculated pistachios (47 µg/g), followed by A. ochraceus (9.6 µg/g) and A. melleus (3.3 µg/g). A. bridgeri did not produce OTA. OTA production by section Circumdati was optimal from 20 to 30°C. All 216 boscalid-resistant isolates from section Nigri were identified as A. tubingensis, and representative isolates (n = 130) produced 3.8 µg/kg OTA in inoculated pistachios. This is the first detailed report on OTA contamination and causal fungi in California pistachios and will be helpful in devising effective management strategies.

Etiology of Botryosphaeria Panicle and Shoot Blight of Pistachio (Pistacia vera) Caused by Botryosphaeriaceae in Italy.

Pistachio (Pistacia vera) is an important crop in Italy, traditionally cultivated in Sicily (southern Italy) for several decades now. In recent years, new orchards have been planted in new areas of the island. Field surveys conducted in 2019 revealed the presence of symptomatic trees showing shoot dieback, cankers, fruit spots, and leaf lesions. Isolations from symptomatic samples consistently yielded fungal species in the Botryosphaeriaceae family. Identification of collected isolates was conducted using morphological and molecular analyses. Morphological characterization was based on conidia measurements of representative isolates and also effects of temperatures on mycelial growth was evaluated. DNA data derived from sequencing the ITS, tef1-α, and tub2 gene regions were analyzed via phylogenetic analyses (maximum parsimony and maximum likelihood). Results of the analyses confirmed the identity of Botryosphaeria dothidea, Neofusicoccum hellenicum, and N. mediterraneum. Pathogenicity tests were conducted on detached twigs and in the fields both on shoots as well as on fruit clusters using the mycelial plug technique. The inoculation experiments revealed that among the Botryosphaeriaceae species identified in this study N. hellenicum (occasionally detected) and N. mediterraneum were the most aggressive based on lesion length on shoots and fruits. N. mediterraneum was the most widespread among the orchards while B. dothidea can be considered a minor pathogen involved in this complex disease of pistachio. Moreover, to our knowledge, this is the first report of N. hellenicum in Italy.

Potential probiotic and food protection role of wild yeasts isolated from pistachio fruits (Pistacia vera).

BACKGROUND: The biotechnological potential of yeasts from nuts such as pistachio, not only for health applications but also for industry use, has been scarcely studied. Interest in the probiotic capability of yeasts has increased in the past years as well as their utilization as food or feed preservatives. Their capabilities as biocontrol against problematic (spoilage or toxigenic) microorganisms or as antioxidants have been revalued. As a result, both abilities would be desirable to develop a new potential probiotic microorganism which could be added to food or feed to improve their properties. RESULTS: Molecular techniques allowed the identification of a total of seven different species and 15 strains. A screening of the probiotic potential of these strains was carried out. It was found that 65% of the strains resisted the gastrointestinal conditions as well as presented a generation time of < 22 h. Additionally, some strains showed better kinetic parameters than Saccharomyces boulardii (positive control). Complementary tests were done to determine their auto-aggregation capacity, cell surface hydrophobicity, behaviour in a sequential simulated digestion, biofilm formation capability and carbon source assimilation. Finally, 67% and 13% of the studied yeasts showed biocontrol and antioxidant activities, respectively. CONCLUSIONS: Diutina rugosa 14 followed by Diutina rugosa 8 were the best wild yeast from Pistacia vera as potential probiotic and in carbon source utilization. However, Hanseniaspora guilliermondii 6 and Aureobasidium proteae 5 could be used to improve food or feed product preservation because of their notable biocontrol and antioxidant capabilities. © 2020 Society of Chemical Industry.

Screening of biological activities of fungi associated with pistachio bark beetle, Chaetoptelius vestitus (Coleoptera, Curculionidae), infesting pistachio cultivations in Tunisia.

AIMS: In this study, we aimed to explore the enzymatic diversity, the entomopathogenic and the antimicrobial potentialities of fungi associated with the pistachio bark beetle, Chaetoptelius vestitus. METHODS AND RESULTS: A total of 40 isolates were screened for enzymatic diversity. Most of them, 92·5%, were able to produce at least two of the screened enzymes. Pathogenic assays performed on C. vestitus showed a high entomopathogenic activity of the isolates Ata_io_1 (A. tamarii), Fve_io_1 (F. verticillioides), Tpi_io_1 (T. pinophilus), Pal_io_1 (P. album), Pbi_io_2 (Penicillium bilaiae) and Pch_io_1 (P. chrysogenum), as based on mean mortality of C. vestitus. A screening of antimicrobial activity using well diffusion method showed that the isolates Tro_io_1 (T. pinophilus), Tat_io_1 (T. atroroseus) and Pch_io_1 (P. chrysogenum) presented the highest antibacterial activity. Furthermore, Mgu_io_1 (M. guilliermondii), Asc_io_1 (A. sclerotiorum), Ata_io_1 (A. tamarii), G. lavendula (Gla_io_1), Pva_io_1 (P. variotii), Pul_io_1 (P. ulaiense), Tat_io_1 (T. atroroseus) and Tro_io_1 (T. roseum) were active against at least two of the three tested fungal phytopathogens. CONCLUSIONS: Fungal isolates representing entomopathogenic activity and a broad spectrum of antimicrobial activities can be considered as promising resources for biological pistachio trees protection. SIGNIFICANCE AND IMPACT OF THE STUDY: Fungi associated with C. vestitus were investigated for detecting their potential biotechnological applications.

Exogenous ß-aminobutyric acid application attenuates Aspergillus decay, minimizes aflatoxin B1 accumulation, and maintains nutritional quality in fresh-in-hull pistachio kernels.

BACKGROUND: Pistachio fruits suffer from postharvest decay, caused by Aspergillus flavus. This results in aflatoxin B1 (AFB1 ) accumulation in kernels, which is hazardous for human health due to its carcinogenic activity. In this study, the mechanism used by exogenous ß-aminobutyric acid (BABA) treatment for attenuating Aspergillus decay, minimizing aflatoxin B1 (AFB1 ) accumulation, and maintaining nutritional quality in fresh-in-hull pistachio kernels, infected by A. flavus during storage at 25 °C for 18 days, was investigated. RESULT: Results of an in vivo assay showed that the spore germination and germ tube elongation of A. flavus was repressed by BABA treatment at 7.5 mM. Aspergillus decay accompanied by AFB1 accumulation was also minimized in fresh-in-hull pistachio kernels treated with BABA at 7.5 mM and infected by A. flavus. Fresh-in-hull pistachio kernels, infected by A. flavus, treated with BABA at 7.5 mM, also exhibited higher phenol and flavonoid accumulation and 2,2-diphenyl-1-picrylhydrazyl (DPPH) scavenging capacity accompanied by higher phenylalanine ammonia lyase (PAL) enzyme activity. CONCLUSION: Promoting phenylpropanoid pathway activity with higher PAL enzyme activity in fresh-in-hull pistachio kernels treated with BABA may not only reduce Aspergillus decay in kernels by cell wall fortification but also may be favorable for maintaining the kernels' nutritional quality through its effects on ROS scavenging capacity. As oxidative stress, represented by ROS accumulation, is responsible for A. flavus growth and AFB1 accumulation, higher phenol and flavonoid accumulation in fresh-in-hull pistachio kernels treated with BABA may be beneficial for attenuating Aspergillus decay and minimizing AFB1 accumulation. © 2019 Society of Chemical Industry.

Phytopathogenic and antagonistic potentialities of fungi associated with pistachio bark beetle, Chaetoptelius vestitus (Coleoptera, Curculionidae), infesting pistachio (Pistacia vera) in Tunisia.

AIM: This study investigated the biodiversity of fungi associated with the pistachio bark beetle, Chaetoptelius vestitus, in Tunisia. We evaluated the phytopathogenic activities and tested antagonistic potentialities with respect to phytopathogens. METHODS AND RESULTS: A total of 41 fungal isolates were randomly isolated from C. vestitus adults and galleries. We identified 28 species belonging to 13 genera using ITS sequences of the ribosomal RNA operons. Pathogenicity assays performed using the excised shoot method revealed that isolates Aal_io_1 (Alternaria alternata), Feq_io_1 (Fusarium equiseti), Fgra_io_1 (Fusarium graminearum), Fve_io_1 (Fusarium verticilloides), Tro_io_1 (Trichothecium roseum) and Nqu_io_1 (Nothophoma quercina) displayed a high pathogenic activity on pistachio stems. Estimation of the antagonistic potentialities of isolated fungi against several phytopathogenic isolates as tested using a dual-culture method showed that isolates Tpi_io_1 (Talaromyces pinophilus), Pbi_io_2 (Penicillium bilaiae), Asc_io_1 (Aspergillus sclerotiorum) and Gla_io_1 (Geosmithia lavendula) displayed a broad range of antagonistic activities. CONCLUSION: Fungi associated with C. vestitus had a variable range of pathogenic activity on pistachio stem. Phytopathogenic fungi were antagonized by different fungal isolates which could be promising in pistachio protection against phytopathogenic fungi. SIGNIFICANCE AND IMPACT OF THE STUDY: This study is the first that investigated the diversity of fungi associated with C. vestitus and evaluated both their phytopathogenic activity and antagonistic potential against fungal phytopathogens.

Effect of gamma irradiation on inactivation of Escherichia coli O157:H7, Salmonella Typhimurium and Listeria monocytogenes on pistachios.

This study evaluated the efficacy of gamma irradiation to inactivate food-borne pathogens on pistachios (Pistacia vera L.). Pistachios inoculated with Escherichia coli O157:H7, Salmonella Typhimurium and Listeria monocytogenes were subjected to gamma irradiation in the range of 0, 0·5, 1, 3 and 5 kGy, and colour change was evaluated after treatment and during storage at room temperature. Pathogen populations decreased with increasing treatment doses. A gamma irradiation dose of 5 kGy decreased the three pathogens on pistachios to under the detection limit (1·0 log CFU per g) without effecting colour change. During storage following treatment, pathogens were reduced due to the postirradiation effect. D-values of pathogens on pistachios showed that L. monocytogenes was more resistant to gamma irradiation than was E. coli O157:H7 or S. Typhimurium. During gamma irradiation treatment, L, a and b values of pistachios did not significantly change but these values changed during storage. These results show that gamma irradiation has potential as a nonthermal process for inactivating food-borne pathogens in pistachios without inducing colour changes. SIGNIFICANCE AND IMPACT OF THE STUDY: Generally, nuts have lower water activity which precludes the growth of food-borne pathogens. But, food-borne outbreaks due to pathogen-contaminated nuts have been reported in the last few decades. Pistachios are one of the most popular nuts and have many health beneficial effects. However, many pasteurization interventions have been used to reduce pathogens on pistachios, but most of them are not effective. This study confirms the effectiveness of gamma irradiation on pasteurization of pistachios. This may be helpful in nut processing industries to ensure the microbial safety of nuts.

Identification and Pathogenicity of Fungal Species Associated with Canker Diseases of Pistachio in California.

A survey was conducted during 2015 and 2016 in pistachio orchards throughout the San Joaquin Valley of California to investigate the occurrence of canker diseases and identify the pathogens involved. Cankers and dieback symptoms were observed mainly in orchards aged >15 years. Symptoms of canker diseases included brown to dark brown discoloration of vascular tissues, wood necrosis, and branch dieback. In total, 58 fungal isolates were obtained from cankers and identified based on multilocus phylogenetic analyses (internal transcribed spacer, glyceraldehyde 3-phosphate dehydrogenase, ß-tubulin, calmodulin, actin 1, and translation elongation factor 1α) representing 11 fungal species: Colletotrichum karstii, Cytospora californica, Cytospora joaquinensis, Cytospora parapistaciae, Cytospora pistaciae, Diaporthe ambigua, Didymella glomerata, Diplodia mutila, Neofusicoccum mediterraneum, Phaeoacremonium canadense, and Schizophyllum commune. Pathogenicity tests conducted in the main pistachio cultivars Kerman, Golden Hills, and Lost Hills using the mycelium-plug method indicated that all fungal species were pathogenic to Pistacia vera. All species tested caused cankers in pistachio branches, although virulence among species varied from high to moderate. Overall, N. mediterraneum and Cytospora spp. were the most widespread and virulent species associated with canker diseases of pistachio in California.

Characterization of Fusarium and Neocosmospora Species Associated With Crown Rot and Stem Canker of Pistachio Rootstocks in California.

California produces 99.1% of pistachios grown in the United States, and diseases affecting pistachio rootstocks represent a constant challenge to the industry. Field surveys of fungi associated with pistachio rootstocks with symptoms of crown rot and stem canker in three central California counties followed by phylogenetic analyses of translation elongation factor 1-α and second largest subunit of RNA polymerase II gene fragments identified three Fusarium species (Fusarium equiseti, Fusarium oxysporum, and Fusarium proliferatum) and two Neocosmospora species (Neocosmospora falciformis and Neocosmospora solani). F. oxysporum and N. falciformis were the fungal species most frequently recovered from symptomatic pistachio trees. Inoculations of detached twigs of cultivar Kerman pistachio Pioneer Gold I and clonal University of California, Berkeley I (UCBI) rootstocks showed that all five species could colonize pistachio wood and cause vascular discolorations. Pathogenicity tests in potted pistachio trees completed Koch's postulates and confirmed that F. oxysporum, F. proliferatum, N. falciformis, and N. solani were capable of producing rot and discoloration in stems of clonal UCBI rootstocks, the most widely planted pistachio rootstock in California. To our knowledge, this study is the first to present insights into the biodiversity and biology of Fusarium and Neocosmospora species associated with pistachio trees in California.

Atoxigenic Aspergillus flavus Isolates Endemic to Almond, Fig, and Pistachio Orchards in California with Potential to Reduce Aflatoxin Contamination in these Crops.

In California, aflatoxin contamination of almond, fig, and pistachio has become a serious problem in recent years due to long periods of drought and probably other climatic changes. The atoxigenic biocontrol product Aspergillus flavus AF36 has been registered for use to limit aflatoxin contamination of pistachio since 2012 and for use in almond and fig since 2017. New biocontrol technologies employ multiple atoxigenic genotypes because those provide greater benefits than using a single genotype. Almond, fig, and pistachio industries would benefit from a multi-strain biocontrol technology for use in these three crops. Several A. flavus vegetative compatibility groups (VCGs) associated with almond, fig, and pistachio composed exclusively of atoxigenic isolates, including the VCG to which AF36 belongs to, YV36, were previously characterized in California. Here, we report additional VCGs associated with either two or all three crops. Representative isolates of 12 atoxigenic VCGs significantly (P < 0.001) reduced (>80%) aflatoxin accumulation in almond and pistachio when challenged with highly toxigenic isolates of A. flavus and A. parasiticus under laboratory conditions. Isolates of the evaluated VCGs, including AF36, constitute valuable endemic, well-adapted, and efficient germplasm to design a multi-crop, multi-strain biocontrol strategy for use in tree crops in California. Availability of such a strategy would favor long-term atoxigenic A. flavus communities across the affected areas of California, and this would result in securing domestic and export markets for the nut crop and fig farmer industries and, most importantly, health benefits to consumers.

Using Allele-specific PCR for detecting multiple amino acid substitutions associated with SDHI resistance in Alternaria alternata causing Alternaria late blight in pistachio.

Alternaria late blight caused by Alternaria alternata is a major disease affecting pistachios grown in California and to some degree those grown in Arizona. Alternaria alternata is prone to quick fungicide resistance selection when single-mode of action fungicides are used. For the specific detection of five possible amino acid alterations associated with Alternaria alternata resistance to succinate dehydrogenase inhibitors used in California and Arizona pistachio orchards, we have designed five primer sets to be used as an allele-specific PCR assay (AS-PCR). Within a couple of hours from DNA extraction, the new specific-primers amplify the different PCR product sizes, according to the chosen target, allowing their differentiation on gel agarose. In our study, the AS-PCR assay consistently detected the mutations H277L and H277R at the AaSdhB gene, the mutations H134R and S135R at the AaSdhC gene, and the mutation D123E at the AaSdhD gene from A. alternata isolates collected from pistachio orchards in California and Arizona. SIGNIFICANCE AND IMPACT OF THE STUDY: This study provides a rapid and cost-effective way to identify five different genotypes associated with Alternaria alternata resistance to succinate dehydrogenase inhibitors fungicides, used to control Alternaria late blight in pistachio. With the allele-specific method developed here, users will be able to identify genotypes with nucleotide substitutions which lead to a reduced sensitivity or resistance selection using a one-step PCR assay, without the use of restriction enzymes which elevates the reaction costs and the chance for errors. In addition, this study formally includes the identification and sequence accession for SdhB-H277L and SdhC-S135R amino acid substitution in A. alternata sampled from California and Arizona pistachio orchards.

Modeling the risk of salmonellosis from consumption of pistachios produced and consumed in the United States.

The risk of salmonellosis from consumption of pistachios produced and consumed in the U.S. was assessed through quantitative microbial risk assessment. Data on Salmonella prevalence and concentration on pistachios, nut crop volume, storage times and temperatures during processing and handling, and reductions during storage or from roasting were derived from laboratory experiments, published literature, and industry expert opinion. Uncertainty was analyzed via what-if scenarios for Salmonella prevalence, concentration, storage reduction, treatment variability, portion of crop treated, and increased consumption. The estimated U.S. incidence of salmonellosis when 100% of pistachios were exposed to a 4 ± 0 log reduction treatment averaged 1.4 cases per billion servings, or <1 case/year, without considering Salmonella decline during storage. Including Salmonella decline during storage reduced the salmonellosis estimates approximately 10-fold. The predicted arithmetic mean number of cases associated with individual 500,000-kg storage silos, contaminated at the highest observed levels, ranged from 5 to 530 when the product was consumed untreated, but was reduced to below 1 case per silo when a 4 ± 0 log reduction treatment was applied. Assuming a uniform 4-log reduction treatment is applied to 100% of the crop and there is no decline of Salmonella during storage, the assessment indicates the following: 10-fold increases in either Salmonella prevalence or concentration, 2-fold increases in both prevalence and concentration, or consumption of >0.05% of untreated product volume yield an arithmetic mean risk of >1 case/year.

Effects of Wound Size, Amount of Sap, and Number of Blighted Nuts on Infection of Pistachio Organs by Neofusicoccum mediterraneum.

Laboratory and field studies were conducted to determine the effects of wounding of nut exocarp, susceptibility period after wounding, and sap nut on infection of pistachio nut by Neofusicoccum mediterraneum, the main causal agent of panicle and shoot blight of pistachio. Under controlled conditions and in the field, detached nuts were inoculated with a conidial suspension 30 min before or after wounding. In addition, a 30-µl drop of pistachio sap was placed on the surface of noninjured nuts 30 min before or after they were wounded and then inoculated. Wounding increased the disease severity under both controlled and field conditions. The addition of sap increased the susceptibility of nuts under controlled conditions but not in the field, possibly due to dried sap blocking the pathogen infection. When nuts of Kerman, Kalehghouchi, and Golden Hills pistachio were wounded and inoculated at different time periods after wounding; the nuts of the three cultivars were highly susceptible to pathogen infection during at least the first 24 h after wounding. Under field conditions, there was not a clear effect of increasing the number of inoculated nuts per panicle or the inoculation position (basal or apical) in killing (blight) of the panicle. Conversely, inoculations conducted with mycelial plugs resulted in higher disease, increased the proportion of dead panicles, and resulted in faster symptom expression than inoculations conducted with a conidial suspension. To determine the temporal infection pattern, leaves and panicles were regularly collected from different orchards from 2004 to 2007 and the pathogen was isolated on medium. Important differences in latent infection were detected between years and orchards, with nut and rachis being, in general, the tissues most susceptible to infection. Results of this study help in better understanding the dynamic of infection and colonization of pistachio by N. mediterraneum.

Bioaugmentation-Assisted Phytostabilisation of Abandoned Mine Sites in South West Sardinia.

Bioaugmentation-assisted phytoremediation implies the administration of selected plant growth promoting bacteria, which significantly improve plant growth and sequestration of heavy metals. In this work, 184 bacterial strains associated with roots of Pistacia lentiscus were isolated from plants spontaneously growing in the abandoned Sardinian mining areas (SW Sardinia, Italy) and phylogenetically characterised. Twenty-one bacterial isolates were assayed for properties relevant for plant growth promotion and metal tolerance. Five different strains, belonging to the genera Novosphingobium, Variovorax, Streptomyces, Amycolatopsis, Pseudomonas, were selected based on their properties for the greenhouse phytoremediation tests. Among the tested inocula, the strain Variovorax sp. RA128A, able to produce ACC deaminase and siderophore, was able to significantly enhance germination and increase length and weight of shoots and roots. Irrespective of the applied treatment, mastic shrub was able to accumulate Cd, Pb and Zn especially in roots.

Molecular identification of potential denitrifying bacteria and use of D-optimal mixture experimental design for the optimization of denitrification process.

Three bacterial strains (TE1, TD3 and FB2) were isolated from date palm (degla), pistachio and barley. The presence of nitrate reductase (narG) and nitrite reductase (nirS and nirK) genes in the selected strains was detected by PCR technique. Molecular identification based on 16S rDNA sequencing method was applied to identify positive strains. In addition, the D-optimal mixture experimental design was used to optimize the optimal formulation of probiotic bacteria for denitrification process. Strains harboring denitrification genes were identified as: TE1, Agrococcus sp LN828197; TD3, Cronobacter sakazakii LN828198 and FB2, Pedicoccus pentosaceus LN828199. PCR results revealed that all strains carried the nirS gene. However only C. sakazakii LN828198 and Agrococcus sp LN828197 harbored the nirK and the narG genes respectively. Moreover, the studied bacteria were able to form biofilm on abiotic surfaces with different degree. Process optimization showed that the most significant reduction of nitrate was 100% with 14.98% of COD consumption and 5.57 mg/l nitrite accumulation. Meanwhile, the response values were optimized and showed that the most optimal combination was 78.79% of C. sakazakii LN828198 (curve value), 21.21% of P. pentosaceus LN828199 (curve value) and absence (0%) of Agrococcus sp LN828197 (curve value).

Evaluation of aqueous and alcohol-based quaternary ammonium sanitizers for inactivating Salmonella spp., Escherichia coli O157:H7, and Listeria monocytogenes on peanut and pistachio shells.

This study evaluated the efficacy of aqueous (aQUAT) and isopropyl alcohol-based quaternary ammonium (ipQUAT) sanitizers for reducing Salmonella spp., Escherichia coli O157:H7, or Listeria monocytogenes populations on peanut and pistachio shell pieces. Inoculated nutshells were mixed with QUAT sanitizers, water, or 70% ethanol and enumerated immediately or after incubation at 30 °C for 48 h. None of the treatments had any immediate effect on Salmonella or E. coli O157:H7 populations on the peanut or pistachio shells. L. monocytogenes populations declined immediately on the peanut and pistachio shells treated with aQUAT or ipQUAT. After incubation, Salmonella and E. coli O157:H7 populations increased significantly on the water- or aQUAT-treated peanut and pistachio shells. L. monocytogenes populations also increased significantly on the water- or aQUAT-treated peanut shells, but levels did not change on the water-treated pistachio shells and levels were just above the limit of detection on the aQUAT-treated pistachio shells. After treatment with ipQUAT and 48-h incubation, Salmonella and E. coli O157:H7 populations decreased to or below the limit of detection on both shell types; L. monocytogenes populations remained at or below the limit of detection on both shell types.

An attempt to model the probability of growth and aflatoxin B1 production of Aspergillus flavus under non-isothermal conditions in pistachio nuts.

Human exposure to aflatoxins in foods is of great concern. The aim of this work was to use predictive mycology as a strategy to mitigate the aflatoxin burden in pistachio nuts postharvest. The probability of growth and aflatoxin B1 (AFB1) production of aflatoxigenic Aspergillus flavus, isolated from pistachio nuts, under static and non-isothermal conditions was studied. Four theoretical temperature scenarios, including temperature levels observed in pistachio nuts during shipping and storage, were used. Two types of inoculum were included: a cocktail of 25 A. flavus isolates and a single isolate inoculum. Initial water activity was adjusted to 0.87. Logistic models, with temperature and time as explanatory variables, were fitted to the probability of growth and AFB1 production under a constant temperature. Subsequently, they were used to predict probabilities under non-isothermal scenarios, with levels of concordance from 90 to 100% in most of the cases. Furthermore, the presence of AFB1 in pistachio nuts could be correctly predicted in 70-81 % of the cases from a growth model developed in pistachio nuts, and in 67-81% of the cases from an AFB1 model developed in pistachio agar. The information obtained in the present work could be used by producers and processors to predict the time for AFB1 production by A. flavus on pistachio nuts during transport and storage.

Novel species of Botryosphaeriaceae associated with shoot blight of pistachio.

Various species of phytopathogenic Botryosphaeriaceae were identified previously from pistachio trees worldwide. Disease symptoms caused by pathogens in Botryosphaeriaceae on pistachio include panicle and shoot blight, leaf defoliation, fruit discoloration and decay. In this study species of Botryosphaeriaceae were collected from blighted pistachio shoots in Arizona, USA, and Greece. The aims of this study were to identify these Botryosphaeriaceae isolates and to test their pathogenicity to pistachio. The fungi were identified based on comparisons of DNA sequence data of the nuclear rDNA internal transcribed spacer region (ITS), a partial translation elongation factor 1-alpha gene (TEF1), a partial ß-tubulin gene (TUB2) and morphological characteristics. Results indicated that some isolates collected from pistachio represent two previously undescribed species, which we described here as Lasiodiplodia americana sp. nov. from the United States and Neofusicoccum hellenicum sp. nov. from Greece. Field inoculations of L. americana and N. hellenicum on branches of four pistachio cultivars showed that both L. americana and N. hellenicum are pathogenic on pistachio. The four pistachio cultivars differed in their susceptibility to the Botryosphaeriaceae species. Results of this study suggested that the two new species of Botryosphaeriaceae need to be monitored carefully to determine the distribution of these pathogens and the possible spread to other areas.

Subtyping of Salmonella Food Isolates Suggests the Geographic Clustering of Serotype Telaviv.

Salmonella is commonly found in a variety of food products and is a major cause of bacterial foodborne illness throughout the world. In this study, we investigated the prevalence and diversity of Salmonella in eight different food types: sheep ground meat, cow ground meat, chicken meat, cow offal, traditional Sanliurfa cheese, unripened feta cheese, pistachios, and isot (a spice blend of dried red peppers specific to Sanliurfa), traditionally and commonly consumed in Turkey. Among 192 food samples, Salmonella was detected in 59 samples, with the highest prevalence in raw poultry parts (58%) and offal (58%) samples, while Salmonella was not detected in pistachios and dried red pepper. Resultant Salmonella isolates were characterized by serotyping, multilocus sequence typing (MLST), and pulsed-field gel electrophoresis (PFGE). Ten different serotypes represented 10 MLST sequence types (STs) with 1 novel ST and 17 PFGE types. Antimicrobial resistance profiling revealed that 30.5% of the isolates were resistant to two or more antimicrobials. Salmonella enterica subsp. enterica serotype Telaviv, which is rare throughout the world, was the second most common serotype isolated from food samples in this study, suggesting that this serotype might be one of the subtypes that is endemic to Turkey.

Low-temperature, low-pressure gas plasma application on Aspergillus brasiliensis, Escherichia coli and pistachios.

AIM: The aim of this study was to investigate the effect of plasma-enhanced chemical vapour deposition (PECVD) treatment on selected bacteria and spores and to contribute to the understanding of the synergistic effect of UV-directed plasma. METHODS AND RESULTS: The experiments were conducted on pure cultures of Aspergillus brasiliensis and Escherichia coli and on naturally contaminated pistachios that were exposed to pure oxygen-, pure argon- and to a mixture of oxygen-argon-generated plasma for different treatment times and at different micro-organism concentrations. Optical emission spectroscopy (OES) measurements were performed to observe the active species in the plasma. After exposure, the effectiveness of decontamination was assessed through microbiological techniques by calculating the growth reduction on a logarithmic scale. A treatment time of 30 min resulted in a 3·5 log reduction of A. brasiliensis using pure oxygen or argon, while treatment times of 5 min, 1 min and 15 s resulted in a 5·4 log reduction using a mixture of argon and oxygen (10 : 1 v/v). Treatment times of 1 min and 30 s resulted in a 4 log reduction of E. coli with oxygen and argon, respectively, which led to a complete elimination of the micro-organisms. Two-log reductions of fungi were achieved for pistachios after a treatment time of 1 min. CONCLUSIONS: These results suggest that this newly designed plasma reactor offers good potential applications for the reduction in micro-organisms on heat-sensitive materials, such as foods. The plasma that was generated with Ar/O2 was more effective than that which was generated with pure oxygen and pure argon. SIGNIFICANCE AND IMPACT OF THE STUDY: An improvement in the knowledge about PECVD mechanisms was acquired from the chemical and biological points of view, and the suitability of the method for treating dry food surfaces was demonstrated.