RESUMEN
This research focused on studying the dynamics of the bacterial pathogen Xylella fastidiosa in almond trees across different developmental stages. The objective was to understand the seasonal distribution and concentration of X. fastidiosa within almond trees. Different tree organs, including leaves, shoots, branches, fruits, flowers, and roots, from 10 X. fastidiosa-infected almond trees were sampled over 2 years. The incidence and concentration of X. fastidiosa were determined using qPCR and isolation. Throughout the study, X. fastidiosa was consistently absent from fruits, flowers, and roots, whereas it was detected in leaves as well as in shoots and branches. We demonstrate that the absence of X. fastidiosa in the roots is likely linked to the inability of this isolate to infect the peach-almond hybrid rootstock GF677. X. fastidiosa incidence in shoots and branches remained consistent throughout the year, whereas in leaf petioles, it varied across developmental stages, with lower detection during the early and late stages of the season. Similarly, viable X. fastidiosa cells were isolated from shoots and branches at all developmental stages, but no successful isolations were achieved from leaf petioles during the vegetative and nut growth stage. Studying the progression of almond leaf scorch symptoms in trees with initial infections showed that once symptoms emerged on one branch, symptomless branches were likely already infected by the bacterium. Therefore, selectively pruning symptomatic branches is unlikely to cure the tree. This study enhances our understanding of X. fastidiosa dynamics in almond trees and may have practical applications for its detection and control.
Asunto(s)
Enfermedades de las Plantas , Hojas de la Planta , Prunus dulcis , Estaciones del Año , Xylella , Xylella/fisiología , Xylella/genética , Enfermedades de las Plantas/microbiología , Prunus dulcis/microbiología , Hojas de la Planta/microbiología , Raíces de Plantas/microbiología , Árboles/microbiología , Brotes de la Planta/microbiología , Flores/microbiología , Frutas/microbiologíaRESUMEN
Outbreak response to quarantine pathogens and pests in the European Union (EU) is regulated by the EU Plant Health Law, but the performance of outbreak management plans in terms of their effectiveness and efficiency has been quantified only to a limited extent. As a case study, the disease dynamics of almond leaf scorch, caused by Xylella fastidiosa, in the affected area of Alicante, Spain, were approximated using an individual-based spatial epidemiological model. The emergence of this outbreak was dated based on phylogenetic studies, and official surveys were used to delimit the current extent of the disease. Different survey strategies and disease control measures were compared to determine their effectiveness and efficiency for outbreak management in relation to a baseline scenario without interventions. One-step and two-step survey approaches were compared with different confidence levels, buffer zone sizes, and eradication radii, including those set by the EU legislation for X. fastidiosa. The effect of disease control interventions was also considered by decreasing the transmission rate in the buffer zone. All outbreak management plans reduced the number of infected trees (effectiveness), but large differences were observed in the number of susceptible trees not eradicated (efficiency). The two-step survey approach, high confidence level, and the reduction in the transmission rate increased the efficiency. Only the outbreak management plans with the two-step survey approach removed infected trees completely, but they required greater survey efforts. Although control measures reduced disease spread, surveillance was the key factor in the effectiveness and efficiency of the outbreak management plans. [Formula: see text] Copyright © 2024 The Author(s). This is an open access article distributed under the CC BY 4.0 International license.
Asunto(s)
Brotes de Enfermedades , Enfermedades de las Plantas , Prunus dulcis , Xylella , Xylella/fisiología , Xylella/genética , Enfermedades de las Plantas/microbiología , Enfermedades de las Plantas/prevención & control , Enfermedades de las Plantas/estadística & datos numéricos , España , Prunus dulcis/microbiología , Hojas de la Planta/microbiología , FilogeniaRESUMEN
KEY MESSAGE: New defense elicitor peptides have been identified which control Xylella fastidiosa infections in almond. Xylella fastidiosa is a plant pathogenic bacterium that has been introduced in the European Union (EU), threatening the agricultural economy of relevant Mediterranean crops such as almond (Prunus dulcis). Plant defense elicitor peptides would be promising to manage diseases such as almond leaf scorch, but their effect on the host has not been fully studied. In this work, the response of almond plants to the defense elicitor peptide flg22-NH2 was studied in depth using RNA-seq, confirming the activation of the salicylic acid and abscisic acid pathways. Marker genes related to the response triggered by flg22-NH2 were used to study the effect of the application strategy of the peptide on almond plants and to depict its time course. The application of flg22-NH2 by endotherapy triggered the highest number of upregulated genes, especially at 6 h after the treatment. A library of peptides that includes BP100-flg15, HpaG23, FV7, RIJK2, PIP-1, Pep13, BP16-Pep13, flg15-BP100 and BP16 triggered a stronger defense response in almond plants than flg22-NH2. The best candidate, FV7, when applied by endotherapy on almond plants inoculated with X. fastidiosa, significantly reduced levels of the pathogen and decreased disease symptoms. Therefore, these novel plant defense elicitors are suitable candidates to manage diseases caused by X. fastidiosa, in particular almond leaf scorch.
Asunto(s)
Regulación de la Expresión Génica de las Plantas , Péptidos , Enfermedades de las Plantas , Prunus dulcis , Xylella , Xylella/patogenicidad , Enfermedades de las Plantas/microbiología , Enfermedades de las Plantas/inmunología , Prunus dulcis/microbiología , Péptidos/farmacología , Péptidos/metabolismo , Ácido Salicílico/metabolismo , Ácido Abscísico/metabolismo , Ácido Abscísico/farmacología , Proteínas de Plantas/genética , Proteínas de Plantas/metabolismo , Resistencia a la Enfermedad , Hojas de la Planta/microbiología , Hojas de la Planta/inmunología , Hojas de la Planta/metabolismo , Hojas de la Planta/genéticaRESUMEN
Strains of the bacterial pathogen Xylella fastidiosa subspecies multiplex (Xfm) and pauca (Xfp) isolated from symptomatic almond and olive plants in Spain and Italy were used in this study. Because of the risk of host jump and considering the importance of southern highbush blueberry production in Spain, we tested a small set of these strains for their potential to infect and cause disease symptoms in blueberries under greenhouse experiments. Xfm IVIA5901 (isolated from almonds in Alicante, Spain) caused symptoms similar to those caused by Xfm AlmaEm3 (isolated from blueberries in Georgia, U.S.A., and used as a reference strain capable of inducing severe symptoms in blueberry). Nevertheless, bacterial populations of Xfm IVIA5901 in planta were significantly lower than those of Xfm AlmaEm3. Xfm ESVL (isolated from almonds, Alicante, Spain) and Xfp XYL1961/18 (isolated from olives, Ibiza Island, Spain) caused limited symptoms, while Xfm XYL466/19 (isolated from wild olives, Mallorca Island, Spain) and Xfm XF3348 (isolated from almonds, Mallorca Island, Spain) and Xfp De Donno (isolated from olives, Puglia, Italy, and representative of the devastating olive quick decline syndrome) did not cause symptoms nor colonize blueberries. This study suggests that certain strains already found in Europe could infect blueberry if conditions conducive for a host jump in this region are met, such as proximity of blueberries to other infected hosts and presence of insect vectors that feed on these crops. Surveys on the presence of X. fastidiosa in blueberries in Spain and other European countries are needed to anticipate possible issues.
Asunto(s)
Arándanos Azules (Planta) , Olea , Enfermedades de las Plantas , Xylella , Xylella/genética , Xylella/fisiología , Arándanos Azules (Planta)/microbiología , Enfermedades de las Plantas/microbiología , Olea/microbiología , España , Italia , Prunus dulcis/microbiologíaRESUMEN
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.
Asunto(s)
Endófitos , Microbiota , Prunus dulcis , Bacterias/genética , Endófitos/genética , Microbiota/genética , Hojas de la Planta/microbiología , Prunus dulcis/microbiologíaRESUMEN
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.
Asunto(s)
Ascomicetos , Prunus dulcis , Fitomejoramiento , Enfermedades de las Plantas/microbiología , Prunus dulcis/genética , Prunus dulcis/microbiologíaRESUMEN
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.
Asunto(s)
Antibiosis , Ascomicetos , Abejas , Flores/microbiología , Prunus dulcis , Animales , Polinización , Estudios Prospectivos , Prunus dulcis/microbiologíaRESUMEN
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.
Asunto(s)
Enfermedades de las Plantas/microbiología , Prunus dulcis , Xylella , Prunus dulcis/microbiología , Xylella/patogenicidad , XilemaRESUMEN
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.
Asunto(s)
Compuestos de Cloro/farmacología , Conservación de Alimentos/métodos , Conservantes de Alimentos/farmacología , Óxidos/farmacología , Prunus dulcis/microbiología , Salmonella enteritidis/efectos de los fármacos , Compuestos de Cloro/química , Conservación de Alimentos/instrumentación , Almacenamiento de Alimentos , Gases/farmacología , Viabilidad Microbiana/efectos de los fármacos , Nueces/microbiología , Óxidos/química , Salmonella enteritidis/crecimiento & desarrolloRESUMEN
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.
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Fungicidas Industriales , Enfermedades de las Plantas , Prunus dulcis , Agentes de Control Biológico , Fungicidas Industriales/farmacología , Enfermedades de las Plantas/prevención & control , Prunus dulcis/microbiologíaRESUMEN
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.
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Microbiología del Aire , Polvo/análisis , Microbiota , Hojas de la Planta/microbiología , Microbiología del Suelo , Viento , Crianza de Animales Domésticos , Animales , California , Enterobacteriaceae/aislamiento & purificación , Escherichia coli/aislamiento & purificación , Aves de Corral , Prunus dulcis/microbiología , ARN Bacteriano/análisis , ARN Ribosómico 16S/análisis , Salmonella/aislamiento & purificación , ÁrbolesRESUMEN
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.
Asunto(s)
Compuestos de Cloro/farmacología , Conservación de Alimentos/métodos , Conservantes de Alimentos/farmacología , Óxidos/farmacología , Ozono/farmacología , Piper nigrum/microbiología , Prunus dulcis/microbiología , Compuestos de Cloro/química , Microbiología de Alimentos , Conservación de Alimentos/instrumentación , Conservantes de Alimentos/química , Gases/química , Gases/farmacología , Listeria monocytogenes/efectos de los fármacos , Listeria monocytogenes/crecimiento & desarrollo , Óxidos/química , Ozono/química , Salmonella enterica/efectos de los fármacos , Salmonella enterica/crecimiento & desarrollo , Semillas/microbiologíaRESUMEN
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.
Asunto(s)
Microbiología de Alimentos/métodos , Lactobacillus plantarum/crecimiento & desarrollo , Preparaciones de Plantas/química , Probióticos/química , Prunus dulcis/química , Recuento de Colonia Microbiana , Manipulación de Alimentos , Almacenamiento de Alimentos , Viabilidad Microbiana , Valor Nutritivo , Polvos/química , Prunus dulcis/microbiología , Semillas/química , Semillas/microbiología , Secado por PulverizaciónRESUMEN
AIMS: To describe the effects of foliar fertilizer application on the bacterial populations of almond tree leaves. METHODS AND RESULTS: We applied a commercially available foliar fertilizer or a water control onto the leaves of almond trees and collected leaves after 1, 7, 14 and 56 days and examined their bacterial populations by 16S rRNA gene sequence analysis. After 1 day, we observed significant differences in 3 of the 4 predominant bacterial phyla, and 5 of the 13 predominant bacterial families. After 7 days, we observed significant differences in all of the predominant phyla, and 8 of the 13 predominant families. After 14 days, the number of significant differences decreased, and after 56 days only 2 of the 13 predominant families differed significantly. CONCLUSIONS: Foliar fertilization significantly altered the bacterial population structure of almond leaves as compared to the water control. While most of the observed perturbation was transient, significant differences remained after 56 days. SIGNIFICANCE AND IMPACT OF THE STUDY: This is the first report describing the effects of foliar fertilization on the bacterial populations of almond leaves and provides new insights as to how this process alters the leaf bacterial population structure.
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Bacterias , Hojas de la Planta/microbiología , Prunus dulcis , Bacterias/clasificación , Bacterias/genética , ADN Bacteriano/análisis , ADN Bacteriano/genética , Prunus dulcis/microbiología , Prunus dulcis/fisiología , ARN Ribosómico 16S/genéticaRESUMEN
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.
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Colletotrichum , Hojas de la Planta , Prunus dulcis , Temperatura , Colletotrichum/fisiología , Enfermedades de las Plantas/microbiología , Hojas de la Planta/microbiología , Prunus dulcis/microbiología , EspañaRESUMEN
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.
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Aflatoxinas , Aspergillus flavus , Ficus , Pistacia , Prunus dulcis , Aflatoxinas/metabolismo , Aspergillus flavus/química , Aspergillus flavus/genética , Aspergillus flavus/fisiología , California , Ficus/microbiología , Contaminación de Alimentos/prevención & control , Interacciones Microbianas , Pistacia/microbiología , Prunus dulcis/microbiologíaRESUMEN
BACKGROUND: Monilinia spp. are responsible for brown rot, one of the most significant stone fruit diseases. Planting resistant cultivars seems a promising alternative, although most commercial cultivars are susceptible to brown rot. The aim of this study was to explore resistance to Monilinia fructicola over two seasons in a backcross one interspecific population between almond 'Texas' and peach 'Earlygold' (named T1E). RESULTS: 'Texas' almond was resistant to brown rot inoculation, whereas peach was highly susceptible. Phenotypic data from the T1E population indicated wide differences in response to M. fructicola. Additionally, several non-wounded individuals exhibited resistance to brown rot. Quantitative trait loci (QTLs) were identified in several linkage groups, but only two proximal QTLs in G4 were detected over both seasons and accounted for 11.3-16.2% of the phenotypic variation. CONCLUSION: Analysis of the progeny allowed the identification of resistant genotypes that could serve as a source of resistance in peach breeding programs. The finding of loci associated with brown rot resistance would shed light on implementing a strategy based on marker-assisted selection (MAS) for introgression of this trait into elite peach materials. New peach cultivars resistant to brown rot may contribute to the implementation of more sustainable crop protection strategies. © 2019 Society of Chemical Industry.
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Ascomicetos/fisiología , Quimera/inmunología , Enfermedades de las Plantas/inmunología , Prunus dulcis/genética , Prunus persica/genética , Quimera/genética , Quimera/microbiología , Resistencia a la Enfermedad , Genotipo , Hibridación Genética , Fitomejoramiento , Enfermedades de las Plantas/microbiología , Enfermedades de las Plantas/prevención & control , Prunus dulcis/inmunología , Prunus dulcis/microbiología , Prunus persica/inmunología , Prunus persica/microbiología , Sitios de Carácter CuantitativoRESUMEN
Almond trees with trunk and branch cankers were observed in several orchards across almond-producing counties in California. Symptoms of cankers included bark lesions, discoloration of xylem tissues, longitudinal wood necrosis, and extensive gumming. Spur and shoot blight associated with rotted fruit were detected in two orchards in Kern County. The fungus Neoscytalidium dimidiatum was consistently recovered from the various cankers, infected fruit, and blighted shoots and its identity was confirmed based on phylogenetic and morphological studies. Phylogenetic analyses of the internal transcribed spacer, translation elongation factor 1-α, and ß-tubulin genes comparing 47 strains from California with reference specimens within the family Botryosphaeriaceae and coupled with detailed morphological observations validated the identity of the pathogenic fungus. Pathogenicity tests conducted in the field using 1- to 2-year-old branches inoculated with mycelium plugs or conidial suspensions and attached fruit inoculated with conidial suspensions fulfilled Koch's postulates. N. dimidiatum appeared highly virulent in almond-producing cankers of up to 22 cm in length within 4 weeks using mycelium plug inoculations as well as severe fruit rot combined with spur blight on the fruit-bearing spurs. This study reports, for the first time, the fungus N. dimidiatum as a pathogen of almond in California causing canker, shoot blight, and fruit rot. Disease symptoms are described and illustrated.
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Ascomicetos/fisiología , Frutas/microbiología , Enfermedades de las Plantas/microbiología , Brotes de la Planta/microbiología , Prunus dulcis/microbiología , Ascomicetos/clasificación , Ascomicetos/genética , California , ADN de Hongos/genética , ADN Espaciador Ribosómico/genética , Proteínas Fúngicas/genética , Micelio/genética , Factor 1 de Elongación Peptídica/genética , Filogenia , Especificidad de la Especie , Tubulina (Proteína)/genéticaRESUMEN
Heat controlled atmosphere (CA) treatments hold potential to pasteurize Salmonella enteritidis PT 30 in almonds. Nonpathogenic Escherichia coli ATCC 25922 was used as a surrogate species of pathogenic Salmonella for validation of thermal pasteurization to meet critical safety requirements. A controlled atmosphere/heating block system (CA-HBS) was used to rapidly determine thermal inactivation of E. coli ATCC 25922. D- and z-values of E. coli ATCC 25922 inoculated in almond powder were determined at four temperatures between 65 °C and 80 °C under different gas concentrations and heating rates. The results showed that D- and z-values of E. coli under CA treatment were significantly (P < 0.05) lower than those under regular atmosphere (RA) treatment at 4 given temperatures. Relatively higher CO2 concentrations (20%) and lower O2 concentrations (2%) were more effective to reduce thermal inactivation time. There were no significant differences in D-values of E. coli when heating rates were above 1 °C/min both in RA and CA treatments. But D-values significantly (P < 0.05) increased under RA treatment and decreased under CA treatment at lower heating rates. Combination of rapid heat and CA treatments could be a promising method for thermal inactivation of S. enteritidis PT 30 in almond powder.
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Escherichia coli/fisiología , Calor , Pasteurización , Prunus dulcis/microbiología , Dióxido de Carbono/farmacología , Recuento de Colonia Microbiana , Seguridad de Productos para el Consumidor , Escherichia coli/efectos de los fármacos , Manipulación de Alimentos , Microbiología de Alimentos , Viabilidad Microbiana , Oxígeno/farmacología , Salmonella enteritidis/efectos de los fármacos , Salmonella enteritidis/fisiología , TermotoleranciaRESUMEN
Almond anthracnose is a serious and emerging disease in several countries. All isolates causing almond anthracnose have been assigned to the Colletotrichum acutatum species complex, of which only C. fioriniae and C. godetiae have been associated with the disease to date. Here, we characterized Colletotrichum isolates from almond fruit affected by anthracnose in the Andalusia region. Two Colletotrichum isolates causing olive anthracnose were included for comparison. Morphological characteristics were useful for separating the isolates into groups based on colony morphology. Pathogenicity tests in almond, olive, and apple fruit showed differences in virulence and some degree of pathogenic specialization among isolates. Molecular characterization allowed clear identification of the Colletotrichum isolates tested. The olive isolates were identified as C. godetiae and C. nymphaeae, both previously identified in Andalusian olive orchards. Two phylogenetic species were identified among the almond isolates: C. godetiae, with gray colonies, which is well known in other countries, and C. acutatum, with pink-orange colonies. This species identification differs from those of pink-colony subpopulations described in other countries, which are C. fioriniae. Therefore, this study is also the first report of a new species of Colletotrichum causing almond anthracnose within the C. acutatum species complex.