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1.
Int J Food Microbiol ; 322: 108575, 2020 Jun 02.
Artigo em Inglês | MEDLINE | ID: mdl-32155515

RESUMO

Apple is a major crop in Argentina where 50% of the production is derived to by-products. Industries process either recently harvested apples or fruit stored for up to 9 months. This crop is susceptible to fungal diseases both external and internal, such as mouldy core (MC). The incidence of fungal pathogens changes during storage, as well as the risk associated with their presence since some contaminants belong to mycotoxigenic genera. The objective of this study was to characterize the fungal contaminants of Red Delicious apple fruit in Argentina evaluating their evolvement from field to process, with main interest on MC causal agents and mycotoxigenic species. A total of 240 apples were analysed; 140, recently harvested and intended for fresh consumption (C), and 100 stored for 9 months in a refrigerated chamber (0-3 °C) and destined to industrialization (I). The 86% of fresh consumption apples showed external fungal lesions, and only 14% were undamaged; MC incidence was 34%. High biodiversity was observed; Penicillium was the predominant genus (54%), followed by Alternaria spp. (41%). Only 3% of industrialization fruit were undamaged, 48% had external lesions and 51% MC. However, biodiversity was lower in these apples. Alternaria spp. was recovered from 60% of apples, mainly causing MC, while Penicillium spp. took second place (34%). All the Alternaria isolates belonged to Section Alternaria with A. tenuissima as the predominant species-group. Alternariol was synthesised by 75% of the isolates, while both alternariol monomethyl-ether and tenuazonic acid by 76%. From the 100 I apples, 93 were contaminated with at least one of these mycotoxins. Alternaria was the main causal agent of MC in Argentinean Red Delicious apples, and fruit affected by this disease might be incorporated into the process line, with a consequent risk of mycotoxin contamination in apple by-products.


Assuntos
Alternaria/isolamento & purificação , Manipulação de Alimentos , Malus/microbiologia , Micotoxinas/metabolismo , Doenças das Plantas/microbiologia , Alternaria/classificação , Alternaria/metabolismo , Argentina , Manipulação de Alimentos/métodos , Microbiologia de Alimentos , Frutas/microbiologia , Fungos/classificação , Fungos/isolamento & purificação
2.
Food Microbiol ; 87: 103382, 2020 May.
Artigo em Inglês | MEDLINE | ID: mdl-31948623

RESUMO

Although due to their acidity some fruit juices are considered safe, several outbreaks have been reported. For processing fruit juices, microwave heating offers advantages such as shorter come-up time, faster and uniform heating, and energy efficiency. Thus, it could be a beneficial alternative to conventional pasteurization. The objective of this study was to study the inactivation kinetics of Escherichia coli O157:H7 and Salmonella Typhimurium under microwave pasteurization at temperatures between 80 and 90 °C, i.e., at conditions that are employed in conventional pasteurization. Inoculated juices were treated at different power levels (600 W, 720 W) and treatment times (5s, 10s, 15s, 20s, 25s). Time-temperature profiles were obtained by fiber-optic sensors in contact with the samples allowing continuous data collection. The log-logistic and Arrhenius equations were used to account for the influence of the temperature history; thus, resulting in two different modeling approaches that were compared in terms of their prediction abilities. Survival kinetics including non-isothermal conditions were described by a non-linear ordinary differential equation that was numerically solved by the Runge-Kutta method (ode45 in MATLAB ®). The lsqcurvefit function (MATLAB®) was employed to estimate the corresponding survival parameters, which were obtained from freshly made apple juice, whereas the prediction ability of these parameters was evaluated on commercial apple juices. Results indicated that inactivation increased with power level, temperature, and treatment time reaching a microbial reduction up to 7 Log10 cycles. The study is relevant to the food industry because it provides a quantitative tool to predict survival characteristics of pathogens at other non-isothermal processing conditions.


Assuntos
Escherichia coli O157/efeitos da radiação , Irradiação de Alimentos/métodos , Sucos de Frutas e Vegetais/microbiologia , Malus/microbiologia , Salmonella typhimurium/efeitos da radiação , Contagem de Colônia Microbiana , Escherichia coli O157/crescimento & desenvolvimento , Irradiação de Alimentos/instrumentação , Micro-Ondas , Salmonella typhimurium/crescimento & desenvolvimento , Temperatura
3.
Food Microbiol ; 87: 103387, 2020 May.
Artigo em Inglês | MEDLINE | ID: mdl-31948628

RESUMO

We evaluated the bactericidal efficacy of the simultaneous application of ultraviolet-A (UV-A) irradiation and fumaric acid (FA) against Escherichia coli O157:H7, Salmonella enterica serovar Typhimurium, and Listeria monocytogenes in apple juice and as well as investigated the effects of this treatment on product quality. Further, we elucidated the mechanisms underlying their synergistic bactericidal action. Simultaneous UV-A light irradiation and 0.1% FA treatment for 30 min resulted in 6.65-, 6.27-, and 6.49-log CFU/ml reductions in E. coli O157:H7, S. Typhimurium, and L. monocytogenes, respectively, which involved 3.15, 2.21, and 3.43 log CFU reductions, respectively, and these were attributed to the synergistic action of the combined treatments. Mechanistic investigations suggested that the combined UVA-FA treatment resulted in significantly greater bacterial cell membrane damage and intracellular reactive oxygen species (ROS) generation. UVA-FA treatment for 30 min did not cause significant changes to the color, nonenzymatic browning index, pH, and total phenolic content of apple juice. These results suggest that combined UVA-FA treatment can be effectively used to control foodborne pathogens in apple juice without affecting its quality.


Assuntos
Antibacterianos/farmacologia , Conservação de Alimentos/métodos , Sucos de Frutas e Vegetais/microbiologia , Fumaratos/farmacologia , Malus/microbiologia , Escherichia coli O157/efeitos dos fármacos , Escherichia coli O157/crescimento & desenvolvimento , Escherichia coli O157/metabolismo , Escherichia coli O157/efeitos da radiação , Conservação de Alimentos/instrumentação , Sucos de Frutas e Vegetais/análise , Listeria monocytogenes/efeitos dos fármacos , Listeria monocytogenes/crescimento & desenvolvimento , Listeria monocytogenes/metabolismo , Listeria monocytogenes/efeitos da radiação , Viabilidade Microbiana/efeitos dos fármacos , Viabilidade Microbiana/efeitos da radiação , Espécies Reativas de Oxigênio/metabolismo , Salmonella typhimurium/efeitos dos fármacos , Salmonella typhimurium/crescimento & desenvolvimento , Salmonella typhimurium/metabolismo , Salmonella typhimurium/efeitos da radiação , Raios Ultravioleta
4.
Food Microbiol ; 87: 103391, 2020 May.
Artigo em Inglês | MEDLINE | ID: mdl-31948632

RESUMO

In the present study, we investigated whether cold plasma activation affected the efficacy of aerosolized hydrogen peroxide against S. Typhimurium and L. innocua. Stem scars and smooth surfaces of grape tomatoes, surfaces of Granny Smith apples and Romaine lettuce (both midrib and upper leaves) and cantaloupe rinds were inoculated with two-strain cocktails of S. Typhimurium and 3-strain cocktails of L. innocua. The inoculated samples were treated with 7.8% aerosolized H2O2 with and without cold plasma for various times. For all fresh produce items and surfaces, cold plasma significantly (P < 0.05) improved the efficacy of aerosolized H2O2 against Salmonella and L. innocua. Without cold plasma activation, H2O2 aerosols only reduced populations of Salmonella by 1.54-3.17 log CFU/piece while H2O2 with cold plasma achieved 2.35-5.50 log CFU/piece reductions of Salmonella. L. innocua was more sensitive to the cold plasma-activated H2O2 than Salmonella. Cold plasma activated H2O2 aerosols reduced Listeria populations by more than 5 log CFU/piece on all types and surfaces of fresh produce except for the tomato stem scar area. Without cold plasma, the reductions by H2O2 were only 1.35-3.77 log CFU/piece. Overall, our results demonstrated that cold plasma activation significantly enhanced the efficacy of H2O2 mist against bacteria on fresh produce.


Assuntos
Cucumis melo/microbiologia , Peróxido de Hidrogênio/farmacologia , Alface/microbiologia , Lycopersicon esculentum/efeitos dos fármacos , Malus/microbiologia , Gases em Plasma/farmacologia , Salmonella typhimurium/efeitos dos fármacos , Vitis/microbiologia , Peróxido de Hidrogênio/química , Lycopersicon esculentum/crescimento & desenvolvimento , Salmonella typhimurium/crescimento & desenvolvimento
5.
Plant Dis ; 104(1): 147-153, 2020 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-31729931

RESUMO

Pseudothecia development stages of Venturia inaequalis (apple scab) were investigated in two climatically different regions in the Western Cape of South Africa. The aim was to determine the pseudothecial density (PD; pseudothecia per fertile lesion [p/f]) and ascal density (AD; asci per pseudothecium [a/p]) that contributes to defining the potential ascospore dose in a common prediction model of the apple scab infection risk. The PD and AD were compared between Elgin (EL), now considered a warm winter apple-growing region because of climate warming, and Koue Bokkeveld (KB), a cold winter region. In 2012 and 2013, scabbed apple leaves were collected during leaf-drop in KB and EL and overwintered either in their region of origin or in the other region. PD was significantly higher in scabbed leaves collected and overwintered in KB (mean, 24.11 p/f) than in leaves collected in KB and overwintered in EL (mean, 17.11 p/f; P < 0.001). PD of scabbed leaves collected and overwintered in EL (mean, 15.27 p/f) or collected in EL and overwintered in KB (mean, 16.07 p/f) did not differ significantly. Ascal density did not differ significantly in any treatment or season. We concluded that the significantly higher PD of scabbed leaves collected from the cooler region of KB and overwintered in KB compared with scabbed leaves collected in EL or KB and overwintered in EL could be caused by adaptations of V. inaequalis populations to the respective climates. This implied long-term effects of climate warming on apple scab epidemiology and management.


Assuntos
Ascomicetos , Modelos Biológicos , Doenças das Plantas , Temperatura , Ascomicetos/fisiologia , Malus/microbiologia , Doenças das Plantas/microbiologia , Folhas de Planta/microbiologia , África do Sul
6.
Plant Dis ; 104(1): 168-178, 2020 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-31697224

RESUMO

Apple scab, caused by Venturia inaequalis, is the most common fruit and foliar disease in commercial apple production worldwide. Early in the production season, preventative contact fungicide sprays are essential for protecting highly susceptible continuously unfolding and expanding young leaves. In South Africa, mancozeb is a key contact fungicide used for controlling apple scab early in the season. The current study developed deposition benchmarks indicative of the biological efficacy of mancozeb against apple scab, using a laboratory-based apple seedling model system. The model system employed a yellow fluorescent pigment that is known to be an effective tracer of mancozeb deposition. A concentration range of mancozeb (0.15 to 1 times the registered dosage) and fluorescent pigment concentrations was sprayed onto seedling leaves, which yielded various fluorescent particle coverage (FPC%) levels. Modeling of the FPC% values versus percent disease control yielded different benchmark values when disease quantification was conducted using two different methods. Thermal infrared imaging (TIRI) disease quantification resulted in a benchmark model where 0.40%, 0.79%, and 1.35 FPC% yielded 50, 75, and 90% apple scab control, respectively. These FPC% values were higher than the benchmarks (0.10, 0.20, and 0.34 FPC%, respectively) obtained with quantitative real-time PCR (qPCR) disease quantification. The qPCR benchmark model is recommended as a guideline for evaluating the efficacy of mancozeb sprays on leaves in apple orchards since the TIRI benchmark model underestimated disease control. The TIRI benchmark model yielded 68% disease control at the lowest mancozeb dosage, yet no visible lesion developed at this dosage. Both benchmark models showed that mancozeb yielded high levels of disease control at very low concentrations; for the qPCR benchmark model the FPC% value of the FPC90 (90% control) corresponded to 0.15 times that of the registered mancozeb concentration in South Africa, i.e., 85% lower than the registered dosage.


Assuntos
Ascomicetos , Malus , Maneb , Doenças das Plantas , Zineb , Ascomicetos/efeitos dos fármacos , Benchmarking , Malus/microbiologia , Maneb/química , Maneb/farmacologia , Doenças das Plantas/prevenção & controle , Folhas de Planta/microbiologia , África do Sul , Zineb/química , Zineb/farmacologia
7.
Plant Dis ; 104(1): 121-128, 2020 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-31730414

RESUMO

Aureobasidium pullulans is used as a biocontrol agent for fire blight protection in organic apple and pear production. We assessed colonization of pome flowers by A. pullulans in orchards located near Corvallis, OR and Wenatchee, WA. Blossom Protect, a mix of A. pullulans strains CF10 and CF40, and its citrate-based companion, Buffer Protect, were sprayed at 70% bloom. Later in bloom, the population size of putative A. pullulans on flowers was estimated by dilution plating; plate scrapings of putative A. pullulans were then sampled and subjected to a PCR analysis. Sequenced PCR amplicons of the internal transcribed spacer region and the elongase gene confirmed the presence of A. pullulans, whereas a multiplex PCR with primers specific to CF10 and CF40 was used to determine the presence of the introduced strains. At Corvallis, a wet spring environment, A. pullulans, was recovered from most (>90%) Bartlett pear and Golden Delicious apple flowers sampled from experimental trees, regardless of whether the trees were treated with Blossom Protect. Nevertheless, population size estimates of A. pullulans on the flowers were correlated with the number of times Blossom Protect was sprayed on the trees. At Wenatchee, an arid spring environment, A. pullulans was detected on most flowers from trees treated with Blossom Protect, but only on a minority of flowers from nontreated controls. In both locations, the combined incidence of strains CF10 and CF40 on flowers averaged 89% on Blossom Protect-treated trees, but only 27% on adjacent, nontreated trees. During subsequent trials, the efficacy of Blossom Protect for fire blight control was compared with alternative yeast isolates, with each applied with Buffer Protect; local isolates of A. pullulans and Cryptococcus neoformans and a postharvest biocontrol strain of Cystofilobasidium infirmominiatum were used All yeast strains suppressed fire blight to a degree; however, in each of four trials, the level of suppression was highest with Blossom Protect, and it was significantly superior (P ≤ 0.05) to other yeast isolates in two of the trials. Because A. pullulans strains CF10 and CF40 were detected primarily on flowers on trees treated with Blossom Protect, and because they were detected much less frequently on nearby nontreated tress, we recommend treating every tree row with Blossom Protect at least once for organic fire blight suppression.


Assuntos
Ascomicetos , Frutas , Malus , Pyrus , Ascomicetos/genética , Ascomicetos/crescimento & desenvolvimento , DNA Fúngico/genética , Frutas/microbiologia , Malus/microbiologia , Interações Microbianas , Doenças das Plantas/microbiologia , Reação em Cadeia da Polimerase , Pyrus/microbiologia
8.
Food Chem ; 302: 125288, 2020 Jan 01.
Artigo em Inglês | MEDLINE | ID: mdl-31419774

RESUMO

The effects of benzothiadiazole (BTH) on Penicillium expansum development, mitochondria energy metabolism, and changes in the number and structure of mitochondria in apple fruit were investigated after the fruit were immersed in 100 mg L-1 BTH for 10 min and then stored at 22 °C. The results indicated that BTH treatment significantly decreased the lesion diameter of fruit challenged with P. expansum; further, treatment enhanced the activities of mitochondrial respiratory metabolism-related enzymes, such as succinate dehydrogenase, cytochrome oxidase, H+-ATPase and Ca2+-ATPase, along with high ATP level and energy status in apple fruit during storage. Moreover, transmission electron microscopy results indicated that BTH treatment was beneficial for maintaining the number and structure of mitochondria during storage. The results suggested that BTH treatment enhanced ATP levels via mitochondrial energy metabolism, which might contribute to the induced resistance in apple fruit during storage.


Assuntos
Metabolismo Energético/efeitos dos fármacos , Armazenamento de Alimentos , Frutas/metabolismo , Malus/efeitos dos fármacos , Malus/metabolismo , Mitocôndrias/efeitos dos fármacos , Tiadiazóis/farmacologia , Frutas/microbiologia , Malus/microbiologia , Mitocôndrias/metabolismo , Penicillium/fisiologia
9.
Int J Food Microbiol ; 313: 108377, 2020 Jan 16.
Artigo em Inglês | MEDLINE | ID: mdl-31670166

RESUMO

The ability of three Penicillium expansum isolates to produce patulin was first evaluated in YES medium after incubation at 25 °C to select a high patulin producer. Then, a spore suspension of the selected P. expansum 3.78 strain was inoculated onto the surface of Golden delicious apples and incubated at 8 or 20 °C until the mold lesion reached a diameter of 1, 2 or 3 cm. For each lesion size, patulin was quantified from apple samples cut into 1 cm depthwise fractions and widthwise sized cylinders. Maximum patulin concentration, about 80,000 ng/g apple, was obtained at 8 °C for the center and surface sample of the 3 cm diameter lesion. Patulin was systematically found at the highest concentration in the lesions, but still quantified up to one centimeter next to the lesion. Patulin concentrations were not significantly different between the 8 and 20 °C incubation temperature, except for the 3 cm large lesions. Based on these findings, and for lesions less than or equal to 3 cm in diameter, we recommend to consumers to cut off at least 1 cm around and below the mold spot to limit patulin exposure. Apples should also be stored at cool temperatures, below 8 °C, to delay lesion development.


Assuntos
Armazenamento de Alimentos/métodos , Frutas/química , Malus/microbiologia , Patulina/análise , Penicillium/metabolismo , Armazenamento de Alimentos/instrumentação , Frutas/microbiologia , Malus/química , Patulina/biossíntese , Penicillium/crescimento & desenvolvimento , Temperatura
10.
Food Microbiol ; 86: 103327, 2020 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-31703855

RESUMO

The study investigated the efficacy of two GRAS-status phytochemicals, mega-resveratrol (RV) and naringenin (NG) to inactivate Escherichia coli O157:H7 (EHEC) in apple cider. A five-strain mixture of EHEC (∼7 log CFU/ml) was inoculated into cider, followed by the addition of RV (8.7 mM and 13.0 mM) or NG (7.3 mM and 11.0 mM). The cider samples were stored at 4 °C for 14 days and EHEC was enumerated on days 0,1,5,7 and 14. The deleterious effects of RV and NG on EHEC cells were visualized by scanning electron microscopy (SEM), and RT-qPCR was done to determine the effect of phytochemicals on three known acid resistance (AR) systems of EHEC. NG was more effective than RV and reduced EHEC counts by ∼4.5 log CFU/ml by day 14, whereas RV reduced counts by ∼2.5 log CFU/ml compared to controls (P < 0.05). SEM showed that RV and NG resulted in the destruction of EHEC cells, and surviving bacteria appeared 'lemon shaped'. RT-qPCR results revealed that RV and NG downregulated the transcription of AR associated genes in EHEC (P < 0.05). Results suggest the potential use of RV and NG as natural antimicrobial additives to enhance the microbiological safety of apple cider. However, sensory analysis studies are warranted.


Assuntos
Escherichia coli O157/efeitos dos fármacos , Flavanonas/farmacologia , Aditivos Alimentares/farmacologia , Conservação de Alimentos/métodos , Sucos de Frutas e Vegetais/microbiologia , Malus/microbiologia , Resveratrol/farmacologia , Escherichia coli O157/crescimento & desenvolvimento , Malus/química , Viabilidade Microbiana/efeitos dos fármacos
11.
Pest Manag Sci ; 76(1): 179-187, 2020 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-31106509

RESUMO

BACKGROUND: Frequent pesticide treatments in fruit orchards increase hazards for workers, consumers and the environment. Moreover, the indiscriminate and excessive use of pesticides often induces resistance in pests. In the past few years, physical exclusion strategies have been proposed as an alternative for the control of insect pests. The goal of this study was to evaluate the effectiveness of anti-hail photoselective netting in protecting apples against key and emerging pests, as well as the impact on beneficial arthropods, fungal diseases and fruit quality. RESULTS: In netted plots, a significant reduction in pest populations, i.e. fruit moths, Halyomorpha halys (Stål) and Drosophila suzukii (Matsumura), was recorded in comparison with un-netted controls. Moreover, the damage on fruits caused by H. halys was reduced up to 62% compared with insecticidal treatments. The net did not negatively affect the abundance of predators and the incidence of post-harvest rot. In addition, the incidence of bitter pit on apple was reduced up to 52%. Furthermore, fruit quality was unaffected by the net coverage (both at harvest and after 4 months of storage). CONCLUSION: Anti-hail photoselective pearl netting proved a promising exclusion system that can prevent attack by more than one insect pest at a time, allowing for a strong reduction in insecticide treatments and relative costs. At the same time, the netting did not negatively influence the presence of predators, the incidence of fungal disease or fruit quality. © 2019 Society of Chemical Industry.


Assuntos
Artrópodes , Malus , Animais , Frutas , Controle de Insetos , Malus/microbiologia , Doenças das Plantas
12.
BMC Plant Biol ; 19(1): 532, 2019 Dec 02.
Artigo em Inglês | MEDLINE | ID: mdl-31791233

RESUMO

BACKGROUND: Although the most common path of infection for fire blight, a severe bacterial disease on apple, is via host plant flowers, quantitative trait loci (QTLs) for fire blight resistance to date have exclusively been mapped following shoot inoculation. It is not known whether the same mechanism underlies flower and shoot resistance. RESULTS: We report the detection of a fire blight resistance QTL following independent artificial inoculation of flowers and shoots on two F1 segregating populations derived from crossing resistant Malus ×robusta 5 (Mr5) with susceptible 'Idared' and 'Royal Gala' in experimental orchards in Germany and New Zealand, respectively. QTL mapping of phenotypic datasets from artificial flower inoculation of the 'Idared' × Mr5 population with Erwinia amylovora over several years, and of the 'Royal Gala' × Mr5 population in a single year, revealed a single major QTL controlling floral fire blight resistance on linkage group 3 (LG3) of Mr5. This QTL corresponds to the QTL on LG3 reported previously for the 'Idared' × Mr5 and an 'M9' × Mr5 population following shoot inoculation in the glasshouse. Interval mapping of phenotypic data from shoot inoculations of subsets from both flower resistance populations re-confirmed that the resistance QTL is in the same position on LG3 of Mr5 as that for flower inoculation. These results provide strong evidence that fire blight resistance in Mr5 is controlled by a major QTL on LG3, independently of the mode of infection, rootstock and environment. CONCLUSIONS: This study demonstrates for the first time that resistance to fire blight caused by Erwinia amylovora is independent of the mode of inoculation at least in Malus ×robusta 5.


Assuntos
Resistência à Doença/genética , Erwinia amylovora/fisiologia , Genes de Plantas , Ligação Genética , Malus/microbiologia , Doenças das Plantas/genética , Flores/microbiologia , Flores/fisiologia , Malus/genética , Doenças das Plantas/microbiologia , Locos de Características Quantitativas
13.
BMC Plant Biol ; 19(1): 579, 2019 Dec 23.
Artigo em Inglês | MEDLINE | ID: mdl-31870310

RESUMO

BACKGROUND: Although it is known that resistant rootstocks facilitate management of fire blight disease, incited by Erwinia amylovora, the role of rootstock root traits in providing systemic defense against E. amylovora is unclear. In this study, the hypothesis that rootstocks of higher root vigor provide higher tolerance to fire blight infection in apples is tested. Several apple scion genotypes grafted onto a single rootstock genotype and non-grafted 'M.7' rootstocks of varying root vigor are used to assess phenotypic and molecular relationships between root traits of rootstocks and fire blight susceptibility of apple scion cultivars. RESULTS: It is observed that different root traits display significant (p < 0.05) negative correlations with fire blight susceptibility. In fact, root surface area partially dictates differential levels of fire blight susceptibility of 'M.7' rootstocks. Furthermore, contrasting changes in gene expression patterns of diverse molecular pathways accompany observed differences in levels of root-driven fire blight susceptibility. It is noted that a singular co-expression gene network consisting of genes from defense, carbohydrate metabolism, protein kinase activity, oxidation-reduction, and stress response pathways modulates root-dependent fire blight susceptibility in apple. In particular, WRKY75 and UDP-glycotransferase are singled-out as hub genes deserving of further detailed analysis. CONCLUSIONS: It is proposed that low root mass may incite resource-limiting conditions to activate carbohydrate metabolic pathways, which reciprocally interact with plant immune system genes to elicit differential levels of fire blight susceptibility.


Assuntos
Erwinia amylovora/fisiologia , Malus/fisiologia , Doenças das Plantas/microbiologia , Resistência à Doença , Genótipo , Malus/imunologia , Malus/microbiologia , Imunidade Vegetal/fisiologia , Raízes de Plantas/microbiologia , Raízes de Plantas/fisiologia
14.
PLoS One ; 14(11): e0224300, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-31693681

RESUMO

Apple scab caused by Venturia inaequalis Cooke (Wint.) is one the important diseases of trade and industrial significance in apple. In present study variability studies in pathogen isolates were studied, which is one of the most important factors for devising management studies of scab disease in apple. Genetic diversity of 30 Venturia inaequalis isolates from 12 districts of two geographical distinct regions of Jammu and Kashmir was calculated based on the allele frequencies of 28 SSR markers and the internal transcribed spacer (ITS) region of the ribosomal DNA. The ITS based characterized sequences were submitted to NCBI GenBank and accession numbers were sanctioned. Dendrogram showed that all the accessions formed 2 main clusters with various degree of sub clustering within the clusters. Analysis based on SSR study reveals that the heterozygosity ranged from 0.0 and 0.5, with an average value of 0.39. The expected heterozygosis or gene diversity (He) ranged from 0.0 to 0.50 with an average of 0.40. The Fst value ranges from 0 to 0.6 with an average of 0.194. Diversity within each population (HS) values ranging from 0.26 to 0.33. Average differentiation among populations (GST) was 0.11 and populations were isolated by significant distance (r 2 = 0.50, P < 0.01). From the AMOVA analysis, 25% of variation was observed among population, 9% among individuals and 66% within individuals observed in the population. Structure analysis grouped isolates into two populations. Principle coordinate analysis explained variation of 36.6% in population 1, 14.30% in population 2 and 13.10% in population 3(Admixture) with 64.07% as overall cumulative percentage of variation. This indicates that extensive short-distance gene flow occurs in Kashmir region that dispersal over longer distances also appears to occur frequently enough to prevent differentiation due to genetic drift. Also it is evident that Jammu and Kashmir most likely has V. inaequalis subpopulations linked to diverse climatic conditions of the Jammu region compared to the mountainous inland Kashmir region. The results of present study would help to understand the genetic diversity of V. inaequalis from Jammu and Kashmir that would lead in the development of more effective management strategies and development of new resistant cultivars through marker-assisted selection.


Assuntos
Ascomicetos/genética , Fluxo Gênico , Malus/microbiologia , Repetições de Microssatélites/genética , Doenças das Plantas/microbiologia , Ascomicetos/isolamento & purificação , Ascomicetos/patogenicidade , DNA Fúngico/genética , DNA Ribossômico/genética , Frequência do Gene , Variação Genética , Índia , Filogenia , Filogeografia
15.
Planta ; 251(1): 20, 2019 Nov 28.
Artigo em Inglês | MEDLINE | ID: mdl-31781986

RESUMO

MAIN CONCLUSION: Certain apple cultivars accumulate to high levels in their nectar and stigma exudate an acidic chitinase III protein that can protect against pathogens including fire blight disease causing Erwinia amylovora. To prevent microbial infections, flower nectars and stigma exudates contain various antimicrobial compounds. Erwinia amylovora, the causing bacterium of the devastating fire blight apple disease, is the model pathogen that multiplies in flower secretions and infects through the nectaries. Although Erwinia-resistant apples are not available, certain cultivars are tolerant. It was reported that in flower infection assay, the 'Freedom' cultivar was Erwinia tolerant, while the 'Jonagold' cultivar was susceptible. We hypothesized that differences in the nectar protein compositions lead to different susceptibility. Indeed, we found that an acidic chitinase III protein (Machi3-1) selectively accumulates to very high levels in the nectar and the stigma exudate of the 'Freedom' cultivar. We show that three different Machi3-1 alleles exist in apple cultivars and that only the 5B-Machi3-1 allele expresses the Machi3-1 protein in the nectar and the stigma exudate. We demonstrate that the 5B-Machi3-1 allele was introgressed from the Malus floribunda 821 clone into different apple cultivars including the 'Freedom'. Our data suggest that MYB-binding site containing repeats of the 5B-Machi3-1 promoter is responsible for the strong nectar- and stigma exudate-specific expression. As we found that in vitro, the Machi3-1 protein impairs growth and biofilm formation of Erwinia at physiological concentration, we propose that the Machi3-1 protein could partially protect 5B-Machi3-1 allele containing cultivars against Erwinia by inhibiting the multiplication and biofilm formation of the pathogen in the stigma exudate and in the nectar.


Assuntos
Quitinases/metabolismo , Erwinia amylovora/fisiologia , Flores/metabolismo , Malus/enzimologia , Malus/microbiologia , Doenças das Plantas/microbiologia , Exsudatos de Plantas/metabolismo , Néctar de Plantas/metabolismo , Alelos , Sequência de Aminoácidos , Antibacterianos/farmacologia , Biofilmes/efeitos dos fármacos , Biofilmes/crescimento & desenvolvimento , Quitinases/química , Resistência à Doença , Erwinia amylovora/efeitos dos fármacos , Erwinia amylovora/crescimento & desenvolvimento , Regulação da Expressão Gênica de Plantas/efeitos dos fármacos , Malus/efeitos dos fármacos , Malus/genética , Especificidade de Órgãos , Proteínas de Plantas/química , Proteínas de Plantas/metabolismo , Regiões Promotoras Genéticas/genética , RNA Mensageiro/genética , RNA Mensageiro/metabolismo , Tabaco/genética
16.
Plant Dis ; 103(12): 3209-3217, 2019 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-31657997

RESUMO

Glomerella leaf spot (GLS) of apple is caused by three different Colletotrichum species complexes. This study evaluated the dispersal of Colletotrichum spores related to GLS temporal progress and defoliation. Spores were monitored by air and water runoff in different plant heights, and the temporal progress of GLS and defoliation were assessed. Spores of the pathogen were first cached in the lower part of the tree closer to the ground, confirming the importance of dead leaves on the ground as main source of primary inoculum. In plots with high primary inoculum, the disease increases exponentially during favorable weather conditions. The highest initial inoculum was found in the lower part of the tree, but the highest rate of the disease progress in the upper.


Assuntos
Colletotrichum , Malus , Brasil , Colletotrichum/fisiologia , Malus/microbiologia , Doenças das Plantas/microbiologia
17.
Plant Dis ; 103(12): 3129-3141, 2019 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-31642736

RESUMO

Canker and wood rot pathogens cause dieback and, in severe cases, the death of young apple trees. Recently, a higher occurrence of cankers was observed on 1-year-old apple trees in the Western Cape Province of South Africa. This study aimed to assess the phytosanitary status of nursery trees and propagation material as possible inoculum sources for canker pathogens. Thirteen 1-year-old apple orchards showing canker or dieback symptoms were sampled. Certified nursery apple trees were collected from four nurseries as well as scion and rootstock mother plant material. Isolations were made from the discoloration observed in the vascular tissue of the plant parts and from asymptomatic material. Possible canker and wood rot species were identified with PCR and sequence comparisons of the relevant gene regions and phylogenetic analyses. Similar canker and wood rot species were isolated from 1-year-old diseased apple trees, nursery apple trees, and the propagation material. Forty-five fungal species associated with canker or wood rot symptoms were identified. The top five most abundant fungal species found causing disease on commercial 1-year-old trees were also found in high numbers causing latent infection in certified apple nursery trees. These species were Didymosphaeria rubi-ulmifolii sensu lato, Diplodia seriata, Schizophyllum commune, Didymella pomorum, and Coniochaeta fasciculata, with D. rubi-ulmifolii sensu lato being the dominant species in both sampling materials. In all, 65% of certified nursery apple trees, 5% of scion shoots used for budding, and 21% of rooted rootstock cuttings from layer blocks had latent infections of canker and wood rot pathogens. Pathogenicity trials were conducted with isolates of 39 species, inoculated onto 2-year-old branches of 14-year-old Golden Delicious trees. All species caused lesions that were significantly longer than the control. This study confirmed the presence of canker and wood rot pathogens in apple propagation material as well as certified nursery apple trees, which will aid the improvement of management practices in nurseries.


Assuntos
Ascomicetos , Malus , Doenças das Plantas , Ascomicetos/classificação , Ascomicetos/genética , Ascomicetos/isolamento & purificação , Malus/microbiologia , Filogenia , Doenças das Plantas/microbiologia , Doenças das Plantas/prevenção & controle , África do Sul , Madeira/microbiologia
18.
Molecules ; 24(20)2019 Oct 13.
Artigo em Inglês | MEDLINE | ID: mdl-31614954

RESUMO

Abstract: Apple tree canker infected by Valsa mali var. mali is a serious and widely distributed disease in China. Saccharothrix yanglingensis Hhs.015 is an endophytic actinomycete isolated from cucumber roots, and it has been proven that this strain is a promising biocontrol agent on apple tree canker in previous studies. The aim of this study was to elucidate the active ingredients in its metabolites. Two pentaene macrolides, WH01 and WH02, were isolated from strain Hhs.015, and their structures were elucidated based on the extensive spectroscopic analysis. WH01 and WH02 were identified as fungichromin and 1'-deoxyfungichromin, among which WH02 is a novel compound. These two compounds showed strong in vitro and in vivo antifungal activity against V. mali. By comparison of the structures of hyphae cells treated by pure compound and fermentation broth, it has been proven that pentaene macrolides are the main active ingredients in the metabolites of strain Hhs.015. This is the first report on the antifungal activity of fungichromin and its analogs on V. mali, and the 28-member pentaene macrolides were also firstly isolated from the genus of Saccharothrix.


Assuntos
Actinobacteria/química , Antifúngicos/química , Cucumis sativus/química , Doenças das Plantas/prevenção & controle , Antifúngicos/isolamento & purificação , Antifúngicos/farmacologia , China , Fermentação , Hifas/efeitos dos fármacos , Malus/efeitos dos fármacos , Malus/microbiologia , Raízes de Plantas
19.
Int J Mol Sci ; 20(18)2019 Sep 18.
Artigo em Inglês | MEDLINE | ID: mdl-31540359

RESUMO

Effector proteins play an important role in the virulence of plant pathogens such as phytoplasma, which are the causative agents of hundreds of different plant diseases. The plant hosts comprise economically relevant crops such as apples (Malus × domestica), which can be infected by 'Candidatus Phytoplasma mali' (P. mali), a highly genetically dynamic plant pathogen. As the result of the genetic and functional analyses in this study, a new putative P. mali effector protein was revealed. The so-called "Protein in Malus Expressed 2" (PME2), which is expressed in apples during P. mali infection but not in the insect vector, shows regional genetic differences. In a heterologous expression assay using Nicotiana benthamiana and Nicotiana occidentalis mesophyll protoplasts, translocation of both PME2 variants in the cell nucleus was observed. Overexpression of the effector protein affected cell integrity in Nicotiana spp. protoplasts, indicating a potential role of this protein in pathogenic virulence. Interestingly, the two genetic variants of PME2 differ regarding their potential to manipulate cell integrity. However, the exact function of PME2 during disease manifestation and symptom development remains to be further elucidated. Aside from the first description of the function of a novel effector of P. mali, the results of this study underline the necessity for a more comprehensive description and understanding of the genetic diversity of P. mali as an indispensable basis for a functional understanding of apple proliferation disease.


Assuntos
Proteínas de Bactérias/genética , Malus/microbiologia , Phytoplasma/fisiologia , Doenças das Plantas/microbiologia , Tabaco/microbiologia , Sequência de Aminoácidos , Proteínas de Bactérias/análise , Proteínas de Bactérias/metabolismo , Sobrevivência Celular , Expressão Gênica , Interações Hospedeiro-Patógeno , Malus/citologia , Phytoplasma/química , Phytoplasma/genética , Phytoplasma/patogenicidade , Protoplastos/citologia , Protoplastos/microbiologia , Alinhamento de Sequência , Tabaco/citologia , Fatores de Virulência/análise , Fatores de Virulência/genética , Fatores de Virulência/metabolismo
20.
Mol Plant Microbe Interact ; 32(10): 1391-1401, 2019 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-31408392

RESUMO

Salicylic acid (SA) is closely related to disease resistance of plants. WRKY transcription factors have been linked to the growth and development of plants, especially under stress conditions. However, the regulatory mechanism of WRKY proteins involved in SA production and disease resistance in apple is not clear. In this study, MdPBS3.1 responded to Botryosphaeria dothidea and enhanced resistance to B. dothidea. Electrophoretic mobility shift assays, yeast one-hybrid assays, and chromatin immunoprecipitation and quantitative PCR demonstrated that MdWRKY46 can directly bind to a W-box motif in the promoter of MdPBS3.1. Glucuronidase transactivation and luciferase analysis further showed that MdWRKY46 can activate the expression of MdPBS3.1. Finally, B. dothidea inoculation in transgenic apple calli and fruits revealed that MdWRKY46 improved resistance to B. dothidea by the transcriptional activation of MdPBS3.1. Viral vector-based transformation assays indicated that MdWRKY46 elevates SA content and transcription of SA-related genes, including MdPR1, MdPR5, and MdNPR1 in an MdPBS3.1-dependent way. These findings provide new insights into how MdWRKY46 regulates plant resistance to B. dothidea through the SA signaling pathway.


Assuntos
Ascomicetos , Resistência à Doença , Regulação da Expressão Gênica de Plantas , Malus , Proteínas de Plantas , Transdução de Sinais , Ascomicetos/fisiologia , Resistência à Doença/genética , Malus/genética , Malus/microbiologia , Proteínas de Plantas/genética , Proteínas de Plantas/metabolismo , Ácido Salicílico/metabolismo , Transdução de Sinais/genética
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