Leaf endophytic microbiomes of different almond cultivars grafted to the same rootstock.

AIMS: We compared the bacterial endophytic communities of three genetically different almond cultivars that were all grafted on the same type of rootstock, growing side by side within a commercial orchard. METHODS AND RESULTS: We examined the diversity of leaf bacterial endophytes using cultivation-independent techniques and assessed the relative abundance of bacterial families. Two of these three cultivars were dominated by Pseudomonadaceae, while the bacterial composition of the third cultivar consisted mainly of Streptococcaceae. CONCLUSIONS: The experimental set up allowed us to analyse the impact of the shoot cultivar on endophytes, minimizing the influence of rootstock, biogeography, and cultivation status. Our data suggest that the shoot cultivar can shape the leaf endophytic community composition of almond trees. SIGNIFICANCE AND IMPACT OF THE STUDY: Our results suggest that the shoot cultivar controls the composition of the foliar bacterial endophytic community of almonds. Overall, our results could provide a first step to develop strategies for a more sustainable almond agriculture.

Susceptibility of Almond (Prunus dulcis) Cultivars to Twig Canker and Shoot Blight Caused by Diaporthe amygdali.

Twenty-five almond cultivars were assessed for susceptibility to Diaporthe amygdali, causal agent of twig canker and shoot blight disease. In laboratory experiments, growing twigs were inoculated with four D. amygdali isolates. Moreover, growing shoots of almond cultivars grafted onto INRA 'GF-677' rootstock were used in 4-year field inoculations with one D. amygdali isolate. In both types of experiments, inoculum consisted of agar plugs with mycelium, which were inserted underneath the bark, and the lesion lengths caused by the fungus were measured. Necrotic lesions were observed in the inoculated almond cultivars in both laboratory and field tests, confirming the susceptibility of all evaluated cultivars to all inoculated isolates of D. amygdali. Cultivars were grouped as susceptible or very susceptible according to a cluster analysis. The relationship between some agronomic traits and cultivar susceptibility was also investigated. Blooming and ripening times were found to be relevant variables explaining cultivar performance related to D. amygdali susceptibility. Late and very late blooming and early and medium ripening cultivars were highly susceptible to D. amygdali. Our results may provide valuable information that could assist in ongoing breeding programs of this crop and in the selection of cultivars for new almond plantations.

Microencapsulation of probiotics in finger millet milk complex to improve encapsulation efficiency and viability.

This study aimed to assess the effectiveness of finger millet milk complex (almond gum with maltodextrin) to encapsulate the isolated Lactobacillus strains. The wall materials were optimized based on its encapsulation efficiency, antioxidant activity, total phenol content and encapsulation yield. The strains were spray-dried at the optimized condition: 120 °C inlet temperature, maltodextrin 30% and almond gum 1.5%. Survival count of microencapsulated Lactobacillus plantarum RS09 and RS23 strains were 7.91 and 7.83 CFU/g respectively. Viability of microencapsulated strains and free cells under low pH, bile salt, simulated gastric juice and intestinal juice were assessed. Strain RS09 exhibited the highest viable count. Addition of almond gum and finger millet milk increased the phenolic content and offered a protective effect to the strains during spray drying. Results also showed that the powders were amorphous with partial irregularities and a smooth surface with less dents. Hence, they could be used as potential encapsulating agents during spray drying.

Floral Microbes Suppress Growth of Monilinia laxa with Minimal Effects on Honey Bee Feeding.

Management of Monilinia laxa, the causal agent of brown rot blossom blight in almond (Prunus dulcis), relies heavily on the use of chemical fungicides during bloom. However, chemical fungicides can have nontarget effects on beneficial arthropods, including pollinators, and select for resistance in the pathogen of concern. Almond yield is heavily reliant on successful pollination by healthy honey bees (Apis mellifera); thus, identifying sustainable, effective, and pollinator-friendly control methods for blossom blight during bloom is desirable. Flower-inhabiting microbes could provide a natural, sustainable form of biocontrol for M. laxa, while potentially minimizing costly nontarget effects on almond pollinators and the services they provide. As pollinators are sensitive to floral microbes and their associated taste and scent cues, assessing effects of prospective biocontrol species on pollinator attraction is also necessary. Here, our objective was to isolate and identify potential biocontrol microbes from an array of agricultural and natural flowering hosts and test their efficacy in suppressing M. laxa growth in culture. Out of an initial 287 bacterial and fungal isolates identified, 56 were screened using a dual culture plate assay. Most strains reduced M. laxa growth in vitro. Ten particularly effective candidate microbes were further screened for their effect on honey bee feeding. Of the 10, nine were found to both strongly suppress M. laxa growth in culture and not reduce honey bee feeding. These promising results suggest a number of strong candidates for augmentative microbial biocontrol of brown rot blossom blight in almond with potentially minimal effects on honey bee pollination.

Divergent abiotic spectral pathways unravel pathogen stress signals across species.

Plant pathogens pose increasing threats to global food security, causing yield losses that exceed 30% in food-deficit regions. Xylella fastidiosa (Xf) represents the major transboundary plant pest and one of the world's most damaging pathogens in terms of socioeconomic impact. Spectral screening methods are critical to detect non-visual symptoms of early infection and prevent spread. However, the subtle pathogen-induced physiological alterations that are spectrally detectable are entangled with the dynamics of abiotic stresses. Here, using airborne spectroscopy and thermal scanning of areas covering more than one million trees of different species, infections and water stress levels, we reveal the existence of divergent pathogen- and host-specific spectral pathways that can disentangle biotic-induced symptoms. We demonstrate that uncoupling this biotic-abiotic spectral dynamics diminishes the uncertainty in the Xf detection to below 6% across different hosts. Assessing these deviating pathways against another harmful vascular pathogen that produces analogous symptoms, Verticillium dahliae, the divergent routes remained pathogen- and host-specific, revealing detection accuracies exceeding 92% across pathosystems. These urgently needed hyperspectral methods advance early detection of devastating pathogens to reduce the billions in crop losses worldwide.

Antimicrobial activity of ClO2 gas against Salmonella Enteritidis on almonds.

Nuts, including almonds, are occasionally contaminated with Salmonella spp. In this study, we used chlorine dioxide (ClO2) gas to inactivate S. enterica subsp. Enterica serovar Enteritidis on almonds. Almonds inoculated with a single strain of S. Enteritidis (8.95 log cfu/mL) were exposed to ClO2 gas generated from 1.0 or 1.5 mL ClO2 solution in a sealed container at 50 or 60 °C (43% relative humidity) for up to 10 h. The concentration of ClO2 gas peaked at 354-510 and 750-786 ppm within 0.5 h upon deposition of 1.0 and 1.5 mL of aqueous ClO2, respectively, and gradually decreased thereafter. Population of S. Enteritidis on almonds treated at 50 °C decreased to 1.70-2.32 log cfu/sample within 1 h of exposure to ClO2 gas and decreased to below the detection limit (1.7 log cfu/sample) at all ClO2 concentrations after 8 h. At 60 °C, the microbial population fell below the detection limit within 1 h, regardless of the volume of ClO2 solution supplied. Microbial survival on almonds treated with ClO2 gas and stored at 12 or 25 °C was observed for up to 8 weeks and the organism was not recovered from the almonds treated for 10 h and stored at 12 °C for 2-8 weeks. The lightness (L value) and redness (a value) of almonds treated for 10 h were not changed by ClO2 gas treatment, but yellowness (b value) increased. Results showed that Salmonella on almonds was successfully inactivated by ClO2 gas treatment and the microbial survival did not occur during storage.

Aggressiveness of Spanish Isolates of Xylella fastidiosa to Almond Plants of Different Cultivars Under Greenhouse Conditions.

The aggressiveness of Spanish isolates of Xylella fastidiosa, representing different sequence types, were studied in almond plants of several cultivars by means of the dynamics of the population levels and symptoms, colonization and spread, and dose-effect relationships. Pathogen dynamics in almond plants under greenhouse conditions showed doubling times of 2.1 to 2.5 days during the exponential growth phase, with a maximum population size of about 35 days postinoculation (dpi). Differences in patterns in population dynamics were observed between sap and xylem tissue after the exponential growth, as population levels in the xylem tissue remained stable while viable cells in sap decreased. Population levels were higher in two upward zones than in the downward zone with respect to the inoculation area. The first symptoms were observed between 20 and 60 dpi, and disease severity increased over time at doubling times of 30 days, with a maximum observed at 120 dpi. Strains tested showed differences in population levels in the cultivars studied and were able to spread with different intensity from contaminated plant parts to new growing shoots after pruning. Two almond isolates showed different performance in dose-effect relationships when inoculated in cultivar Avijor. Whereas IVIA 5387.2 reached high population levels but showed high median effective dose (ED50) and minimal infective dose (MID) values, IVIA 5901.2 showed low population levels and low ED50 and MID values. This study has implications for the epidemiology of X. fastidiosa in almond crops, estimating doubling times of the pathogen in planta and of symptom development and showing differences in aggressiveness between strains.

Evaluation of Pruning Wound Protection Products for the Management of Almond Canker Diseases in California.

Almond trunk and branch canker diseases constitute a major cause of tree mortality in California. Numerous fungal pathogens have been associated with these canker diseases and pruning wounds act as major infection courts. Before this study, there were no products registered in California for the management of these diseases. In this study, fungicidal products including synthetic chemistries, biocontrols, paint, and a sealant were evaluated for preventing fungal pathogen infection via pruning wounds. In four field trials conducted over two dormant seasons, 16 pruning wound treatments were tested using handheld spray applications against five almond canker pathogens, namely Botryosphaeria dothidea, Neofusicoccum parvum, Cytospora sorbicola, Ceratocystis destructans, and Eutypa lata. The fungicide thiophanate-methyl (Topsin M; United Phosphorus, Bandra West, Mumbai, India) provided 82% overall disease prevention against four fungal pathogens. The biological control agent, Trichoderma atroviride SC1 (Vintec; Bi-PA, Londerzeel, Belgium), tested at three application rates, resulted in 90 to 93% protection of pruning wounds in field trials, and for individual pathogens ranged from 81 to 100% protection for the three rates. At the time of this publication, Vintec is being considered for registration as a biological control product for the prevention of almond canker diseases, while Topsin M is recommended to growers for the prevention of almond canker diseases. This research indicates that effective protection of pruning wounds from infection by almond canker pathogens can be achieved with a one-time spray application of thiophanate-methyl or the biocontrol T. atroviride SC1 (recommended 2 g/liter) after pruning.

Development of an Antifungal Device Based on Oriental Mustard Flour to Prevent Fungal Growth and Aflatoxin B1 Production in Almonds.

The present study describes the manufacture of an antifungal device composed of oriental mustard flour and hydroxyethyl-cellulose (H-OMF) and evaluates its efficacity in inhibiting Aspergillus flavus growth and aflatoxin B1 (AFB1) production in almonds. Additionally, it compares the H-OMF with allyl isothiocyanate (AITC) and a freeze-dried extract of yellow mustard flour (YMF-E); such substances were previously described as antifungal. Minimum inhibitory concentration (MIC), Minimum fungicidal concentration (MFC), the H-OMF in vitro antifungal activity, and the residual fungal population, as well as the production of AFB1 in almonds were determined. AITC and YMF-E showed significant antifungal activity in vitro. Additionally, the in vitro activity of H-OMF avoided mycelial growth by applying 30 mg/L. Almonds treated with AITC (5.07, 10.13, and 20.26 mg/L) and H-OMF (2000 and 4000 mg/L) showed a reduction in the population of A. flavus and the production of AFB1 to values below the limit of detection. YMF-E showed effectiveness by in vitro methodologies (MIC and MFC) but did not show efficacy when applied in almonds. Our findings indicated that the hydroxyethyl-cellulose-based device containing oriental mustard flour might be utilised as a fumigant to increase the safety of almonds and could be extended to other cereals or dry fruits.

Phylogenetic inference enables reconstruction of a long-overlooked outbreak of almond leaf scorch disease (Xylella fastidiosa) in Europe.

The recent introductions of the bacterium Xylella fastidiosa (Xf) into Europe are linked to the international plant trade. However, both how and when these entries occurred remains poorly understood. Here, we show how almond scorch leaf disease, which affects ~79% of almond trees in Majorca (Spain) and was previously attributed to fungal pathogens, was in fact triggered by the introduction of Xf around 1993 and subsequently spread to grapevines (Pierce's disease). We reconstructed the progression of almond leaf scorch disease by using broad phylogenetic evidence supported by epidemiological data. Bayesian phylogenetic inference predicted that both Xf subspecies found in Majorca, fastidiosa ST1 (95% highest posterior density, HPD: 1990-1997) and multiplex ST81 (95% HPD: 1991-1998), shared their most recent common ancestors with Californian Xf populations associated with almonds and grapevines. Consistent with this chronology, Xf-DNA infections were identified in tree rings dating to 1998. Our findings uncover a previously unknown scenario in Europe and reveal how Pierce's disease reached the continent.

Investigation of decontamination effect of argon cold plasma on physicochemical and sensory properties of almond slices.

Cold plasma is a novel technology for surface decontamination. Almond slices can be contaminated with different microorganisms during their production. In the current research, the atmospheric argon plasma treatment (5, 10, 15, and 20 min) was used to decontamination of almond slices surface. Microbial load, Color, peroxide value, hardness, and sensory properties of slices was comprised with untreated samples (control). Descriptive sensory evaluation about color, flavor, crispiness, crunchiness, and hardness of almond slices were performed. According to the results of the microbial tests, Total count, molds and yeasts, and Staphylococcus aureus of almond surface decreased about 2.95 log cfu/g, 1.81 log cfu/g, and 2.72 log cfu/g after 20 min of plasma treatment, respectively, provided that microbial reduction increased more by increasing the treatment time. Coupled with the color evaluation, peroxide value and sensory attributes didn't change during plasma treatment. Having said that, the hardness of slices was changed by increasing treatment time. Furthermore, Principal Component Analysis and cluster analysis were performed for sensory evaluation. In light of the consumer's point of view, firstly 10 min and secondly 15 min plasma treatment can be more desirable.

Gaseous antimicrobial treatments to control foodborne pathogens on almond kernels and whole black peppercorns.

Gaseous treatments with ClO2 and O3 on low-moisture foods (LMFs) have been reported for their efficient bacterial reduction without affecting the external quality of food. However, these studies were conducted on a small scale, which limits their application to LMF industries. We aimed to evaluate the effectiveness of gaseous antimicrobial intervention with ClO2 or O3 to reduce foodborne pathogens (Shiga toxin-producing Escherichia coli, serovars of Salmonella enterica, and Listeria monocytogenes) inoculated on almonds and peppercorns maintained under various conditions. Almonds were treated for over 4 or 6 h. Peppercorns were treated for over 2.5 or 4 h. Gaseous O3 treatment was used for 6 h on almonds and 2 or 4 h on peppercorns. Additionally, the effects of relative humidity (RH) during the treatment of peppercorns and post-treatment heating on almonds were evaluated. Heating at 65 °C post-ClO2 treatment yielded the highest bacterial log reduction of 4.6 CFU/g on almonds, while 80% RH resulted in 3.7-log bacterial reduction on peppercorns. Gaseous O3 resulted in maximum log reductions of 1.3 and 2.5 CFU/g on almonds and peppercorns, respectively. No visual damage was observed. In conclusion, ClO2 was more efficient than O3 and the treatment can be incorporated into industrial practices.

Physicochemical and microstructural properties and probiotic survivability of symbiotic almond yogurt alternative using polymerized whey protein as a gelation agent.

A plain symbiotic almond yogurt-like product was formulated and developed using a plant-based starter YF-L02 (Streptococcus thermophilus, Lactobacillus delbrueckii subsp. bulgaricus supplemented with Lactobacillus acidophilus, Lactobacillus paracasei, and Bifidobacterium animalis) and inulin; 0.6% polymerized whey protein (PWP), 0.3% pectin, and 0.05% xanthan gum were optimized for the formula of the almond yogurt alternative. Two groups with/without calcium citrate and vitamin D2 were prepared and analyzed for chemical composition, changes in pH, viscosity, and probiotic survivability during storage at 4 °C for 10 weeks. The results showed that (1) over 10 weeks storage, the differences in the pH, viscosity, and probiotic survivability between the control and the fortified samples were not significant (P > 0.05); (2) the pH of both yogurt samples decreased 0.2 units while their viscosity slightly increased during storage; (3) the populations of L. paracasei and B. animalis remained above 106 cfu/g during the storage, whereas the population of L. acidophilus decreased dramatically during the first 4 weeks, especially the control group; (4) the microstructure was examined by scanning electron microscopy, revealing a compact and denser gel structure formed by 0.6% PWP with the presence of 0.3% pectin and 0.05% xanthan gum. In conclusion, PWP might be a proper gelation agent for the formulation of symbiotic almond yogurt alternative. PRACTICAL APPLICATION: In this study, polymerized whey protein was used as a gelation agent to formulate symbiotic almond yogurt alternatives with comparable physical texture and probiotic survivability to dairy yogurt during storage. This technology may be used for the development of plant-based fermented foods.

HPLC-MS/MS Method for the Detection of Selected Toxic Metabolites Produced by Penicillium spp. in Nuts.

Penicillium spp. are emerging as producers of mycotoxins and other toxic metabolites in nuts. A HPLC-MS/MS method was developed to detect 19 metabolites produced by Penicillium spp. on chestnuts, hazelnuts, walnuts and almonds. Two extraction methods were developed, one for chestnuts and one for the other three nuts. The recovery, LOD, LOQ and matrix effect were determined for each analyte and matrix. Correlation coefficients were always >99.99%. In walnuts, a strong signal suppression was observed for most analytes and patulin could not be detected. Six strains: Penicillium bialowiezense, P. brevicompactum, P. crustosum, P. expansum, P. glabrum and P. solitum, isolated from chestnuts, were inoculated on four nuts. Chestnuts favored the production of the largest number of Penicillium toxic metabolites. The method was used for the analysis of 41 commercial samples: 71% showed to be contaminated by Penicillium-toxins. Cyclopenin and cyclopenol were the most frequently detected metabolites, with an incidence of 32% and 68%, respectively. Due to the risk of contamination of nuts with Penicillium-toxins, future studies and legislation should consider a larger number of mycotoxins.

Microorganisms Move a Short Distance into an Almond Orchard from an Adjacent Upwind Poultry Operation.

Over a 2-year period, drag swabs of orchard soil surface and air, soil, and almond leaf samples were collected in an almond orchard adjacent to (35 m from the first row of trees) and downwind from a poultry operation and in two almond orchards (controls) that were surrounded by other orchards. Samples were evaluated for aerobic plate count, generic Escherichia coli, other coliforms, the presence of Salmonella, bacterial community structure (analyzed through sequencing of the 16S rRNA gene), and amounts of dry solids (dust) on leaf surfaces on trees 0, 60, and 120 m into each orchard. E. coli was isolated from 41 of 206 (20%) and 1 of 207 (0.48%) air samples in the almond-poultry and control orchards, respectively. Salmonella was not isolated from any of the 529 samples evaluated. On average, the amount of dry solids on leaves collected from trees closest to the poultry operation was more than 2-fold greater than from trees 120 m into the orchard or from any of the trees in the control orchards. Members of the family Staphylococcaceae-often associated with poultry-were, on average, significantly (P < 0.001) more abundant in the phyllosphere of trees closest to the poultry operation (10% of relative abundance) than in trees 120 m into the orchard (1.7% relative abundance) or from any of the trees in control orchards (0.41% relative abundance). Poultry-associated microorganisms from a commercial operation transferred a short distance into an adjacent downwind almond orchard.IMPORTANCE The movement of microorganisms, including foodborne pathogens, from animal operations into adjacent plant crop-growing environments is not well characterized. This study provides evidence that dust and bioaerosols moved from a commercial poultry operation a short distance downwind into an almond orchard and altered the microbiome recovered from the leaves. These data provide growers with information they can use to assess food safety risks on their property.

Spray drying and storage of probiotic-enriched almond milk: probiotic survival and physicochemical properties.

BACKGROUND: The combination of the nutritional profile of almond milk with the benefits of probiotic bacteria is an interesting development to meet the demand for sustainable and health-promoting food. Almond milk inoculated with probiotic Lactobacillus plantarum (ATCC8014) was spray dried and the almond, its milk, and powders were characterized physicochemically. Samples were characterized in terms of bacterial survival before and after atomization. Bacterial viability and total fatty acid changes were studied during 8 months' storage at 4 and 22 °C. RESULTS: Results showed adequate physicochemical properties and an optimal bacterial survival rate, maintaining almost the same values before and after the spray-drying operation. A decrease was observed in the cell viability for samples stored at 4 °C. However, the cell count was maintained above the minimum level suggested (107 living cells) to allow potential probiotic functionality for 8 months. On the other hand, the count cell of powders stored at 22 °C was below the minimum level required after 6 months. The fatty acids profile was not significantly (P > 0.05) affected by storage time and temperature. CONCLUSION: A new almond-based-product with probiotics was developed to meet consumer demands. Almond nutrients were recovered from almond milk powder and were found to be a good source of K and high in Mg and in monounsaturated fat. The viability of bacteria was assured during 8 months of storage at 4 °C and up to 6 months for samples stored at 22 °C. © 2020 Society of Chemical Industry.

Effectiveness of Nitrogen Dioxide Fumigation for Microbial Control on Stored Almonds.

ABSTRACT: Quality of stored almonds is compromised by insect infestations and microbial contamination. Nitric oxide (NO) is a potent fumigant for postharvest pest control on fresh and stored products. NO fumigation must be conducted under ultralow oxygen conditions, and it always produces nitrogen dioxide (NO2), depending on the O2 level in the fumigation chamber. NO and NO2 have proven antimicrobial effects but have not been tested for efficacy against microbes in almonds. We evaluated, in this study, fumigation of unpasteurized almonds with NO2 at different levels for inhibition of bacteria and fungi. Almonds were fumigated with 0.1, 0.3, or 1.0% NO under ambient O2 to generate 0.1, 0.3, or 1.0% NO2 conditions; the fumigation treatments lasted 1 or 3 days at 25°C. GreenLight rapid enumeration tests on diluted wash-off almond samples from NO2 fumigation treatments showed either greatly reduced microbial loads or complete control of microorganisms, depending on NO2 concentration and treatment duration. NO2 fumigation was more effective against fungi than against bacteria. These results suggest that postharvest NO fumigation with proper levels of NO and NO2 can be used for insect and microorganism control on stored almonds.

Effect of post inoculation drying procedures on the reduction of Salmonella on almonds by thermal treatments.

Since two outbreaks of salmonellosis were linked to the consumption of almonds in 2001 and 2004, the study of pathogen inactivation kinetics in almonds has been encouraged, often by conducting inoculated challenge studies. The inoculation method could affect the results of such challenge studies, because of the possible increase of moisture on the almonds resulting from a wet inoculation procedure, which may result in a potential overestimation of the effectiveness of treatments used to pasteurize almonds in industrial settings. Salmonella enterica serotype Enteritidis phage type 30 (PT30) isolated from an almond-linked outbreak was inoculated on nonpareil almonds and dried by accelerated (drying the inoculated almonds at 37 °C for 12 h) and conventional (drying inoculated almonds overnight at room temperature) drying methods, before treating the almonds with hot water (blanching) at 88 °C or hot oil (oil roasting) at 127 °C. The Weibull model explained the death of this pathogen on almonds better than log-linear model for oil roasting, whereas both log-linear and Weibull models were similarly effective for blanching. For blanching, the D values for Salmonella Enteritidis PT30 were 12.7 and 10.7 s with accelerated and conventional drying, respectively. For oil roasting, the b-values were 4.59 and 4.18 s with accelerated and conventional drying, respectively. Based on the models, it was concluded that the accelerated drying process resulted in a significantly smaller reduction in Salmonella Enteritidis PT30 on almonds in comparison to conventional drying for both blanching and roasting. Although conventional drying led to significantly lower D or b - values (depending on the model), this difference is not likely to affect the current processing parameters used by the almond industry.

Interaction of Gaseous Chlorine Dioxide and Mild Heat on the Inactivation of Salmonella on Almonds.

The interactive effects of mild heat and gaseous chlorine dioxide (ClO2) on populations of Salmonella on almonds were studied. Almonds, dip inoculated with a two-strain cocktail of attenuated Salmonella Typhimurium, were treated with three concentrations of ClO2 at ambient temperature (ca. 22°C), and at 45, 50, 55, and 60°C for 4 h and with more than 90% relative humidity. Concentrations of ClO2 during treatments were measured, and populations of Salmonella were determined following treatments. Results demonstrated that ClO2 at concentrations of more than 4 mg/L and ambient temperature only reduced populations of Salmonella by 1.46 log CFU/g. With increasing treatment temperature, the efficacy of gaseous ClO2 increased. At 55 and 60°C, >1 mg/L ClO2, and a 4-h treatment time, >4 log CFU/g Salmonella was inactivated. Reductions greater than 4 log of the bacterium by gaseous ClO2 at 55°C were confirmed using a three-strain cocktail of pathogenic Salmonella. Overall, results demonstrated that mild heating is necessary for gaseous ClO2 to achieve more than 4 log CFU/g inactivation of Salmonella on almonds.

Effects of Cultivar Susceptibility, Fruit Maturity, Leaf Age, Fungal Isolate, and Temperature on Infection of Almond by Colletotrichum spp.

Almond anthracnose, caused by Colletotrichum spp., is a reemerging disease in Spain. To date, little research has been conducted on the factors affecting this disease development. In this study, the effects of cultivar, fruit wounding and maturity, leaf age, fungal isolate, and temperature on almond infection by Colletrotrichum spp. were evaluated under laboratory-controlled conditions. Inoculations were performed using conidial suspensions of Colletrotrichum acutatum or C. godetiae. Disease severity was higher in wounded than in unwounded fruit. Based on observations of inoculated fruit, Ferraduel and Nonpareil were the most tolerant cultivars, while Tarraco and Penta were the most susceptible cultivars. Four categories of susceptibility (highly susceptible, susceptible, moderately susceptible, and resistant) were distinguished by using the cluster analysis statistical approach. Differences in susceptibility between young and old leaves were observed, but Nonpareil was consistently the most tolerant cultivar. Significant differences in virulence between C. acutatum and C. godetiae were observed in inoculated fruit, with C. acutatum being the most virulent. Disease development was more severe when inoculations were performed at the fruitlet stage or when the fruit were incubated at approximately 25°C, with respect to other maturity stages and temperatures evaluated. Natural fruit infections were also assessed. Cultivar susceptibility data were compared between laboratory tests and field observations. A significant positive linear correlation was obtained between the susceptibility of the common cultivars evaluated under the two conditions.