Publications by authors named "Neus Teixidó"

32 Publications

Global analysis of the apple fruit microbiome: are all apples the same?

Environ Microbiol 2021 Mar 18. Epub 2021 Mar 18.

Department of Postharvest Science, Agricultural Research Organization, The Volcani Institute, P.O. Box 15159, Rishon LeZion, 7505101, Israel.

We present the first worldwide study on the apple (Malus × domestica) fruit microbiome that examines questions regarding the composition and the assembly of microbial communities on and in apple fruit. Results revealed that the composition and structure of the fungal and bacterial communities associated with apple fruit vary and are highly dependent on geographical location. The study also confirmed that the spatial variation in the fungal and bacterial composition of different fruit tissues exists at a global level. Fungal diversity varied significantly in fruit harvested in different geographical locations and suggests a potential link between location and the type and rate of postharvest diseases that develop in each country. The global core microbiome of apple fruit was represented by several beneficial microbial taxa and accounted for a large fraction of the fruit microbial community. The study provides foundational information about the apple fruit microbiome that can be utilized for the development of novel approaches for the management of fruit quality and safety, as well as for reducing losses due to the establishment and proliferation of postharvest pathogens. It also lays the groundwork for studying the complex microbial interactions that occur on apple fruit surfaces.
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http://dx.doi.org/10.1111/1462-2920.15469DOI Listing
March 2021

Rhizosphere microorganisms enhance in vitro root and plantlet development of Pyrus and Prunus rootstocks.

Planta 2021 Mar 14;253(4):78. Epub 2021 Mar 14.

IRTA Plant In Vitro Culture Laboratory, Fruticulture Programme, Parc Científic I Tecnològic Agroalimentari de Lleida, 25003, Lleida, Catalonia, Spain.

Main Conclusion: The in vitro application of rhizosphere microorganisms led to a higher rooting percentage in Pyrus Py12 rootstocks and increased plant growth of Pyrus Py170 and Prunus RP-20. The rooting of fruit tree rootstocks is the most challenging step of the in vitro propagation process. The use of rhizosphere microorganisms to promote in vitro rooting and plant growth as an alternative to the addition of chemical hormones to culture media is proposed in the present study. Explants from two Pyrus (Py170 and Py12) rootstocks and the Prunus RP-20 rootstock were inoculated with Pseudomonas oryzihabitans PGP01, Cladosporium ramotenellum PGP02 and Phoma sp. PGP03 following two different methods to determine their effects on in vitro rooting and plantlet growth. The effects of the microorganisms on the growth of fully developed Py170 and RP-20 plantlets were also studied in vitro. All experiments were conducted using vermiculite to simulate a soil system in vitro. When applied to Py12 shoots, which is a hard-to-root plant material, both C. ramotenellum PGP02 and Phoma sp. PGP03 fungi were able to increase the rooting percentage from 56.25% to 100% following auxin indole-3-butyric acid (IBA) treatment. Thus, the presence of these microorganisms clearly improved root development, inducing a higher number of roots and causing shorter roots. Better overall growth and improved stem growth of treated plants was observed when auxin treatment was replaced by co-culture with microorganisms. A root growth-promoting effect was observed on RP-20 plantlets after inoculation with C. ramotenellum PGP02, while P. oryzihabitans PGP01 increased root numbers for both Py170 and RP-20 and increased root growth over stem growth for RP-20. It was also shown that the three microorganisms P. oryzihabitans PGP01, C. ramotenellum PGP02 and Phoma sp. PGP03 were able to naturally produce auxin, including indole-3-acetic acid (IAA), at different levels. Overall, our results demonstrate that the microorganisms P. oryzihabitans PGP01 and C. ramotenellum PGP02 had beneficial effects on in vitro rooting and plantlet growth and could be applied to in vitro tissue culture as a substitute for IBA.
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http://dx.doi.org/10.1007/s00425-021-03595-3DOI Listing
March 2021

Field validation of biocontrol strategies to control brown rot on stone fruit in several European countries.

Pest Manag Sci 2021 May 7;77(5):2502-2511. Epub 2021 Feb 7.

IRTA, Postharvest Programme, Edifici Fruitcentre, Parc Científic i Tecnològic Agroalimentari de Lleida, Lleida, Spain.

Background: Brown rot caused by Monilinia spp. is the most significant disease of stone fruit. New approaches to fruit production have necessitated the development of control strategies that are more eco- and consumer-friendly. An efficient field strategy to control brown rot was previously designed based on the application of two biocontrol agents (BCAs), Bacillus amyloliquefaciens CPA-8 (CPA-8) or Penicillium frequentans 909 (Pf909), with calendar-based treatment. In the present study, the strategy was validated on different stone fruit hosts in four producing countries over two seasons.

Results: The results obtained were reported according to three different scenarios: Scenario 1, in which there was no presence of disease in the field; Scenario 2, in which high disease pressure occurred in the field and treatments (biologicals or chemicals) were not effective; and Scenario 3, with low or medium to high disease presence. The results were successful because, in general, BCA strategies were shown to control brown rot to a similar extent as chemicals strategies. We found that most of the trials conducted in this study were classed under Scenario 3 (62.5%), with only 12.5% and 25% of the trials classed under Scenarios 1 and 2, respectively.

Conclusion: These novel findings allowed the formulation of CPA-8 and Pf909 as valuable tools for farmers to produce stone fruits more competitively and meet consumer demand for safer and more environmentally friendly products. © 2021 Society of Chemical Industry.
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http://dx.doi.org/10.1002/ps.6281DOI Listing
May 2021

Depicting the battle between nectarine and : the fruit developmental stage dictates the effectiveness of the host defenses and the pathogen's infection strategies.

Hortic Res 2020 1;7:167. Epub 2020 Oct 1.

IRTA, XaRTA-Postharvest, Edifici Fruitcentre, Parc Científic i Tecnològic Agroalimentari de Lleida, 25003 Lleida, Catalonia Spain.

Infections by the fungus , the main cause of brown rot in Europe, result in considerable losses of stone fruit. Herein, we present a comprehensive transcriptomic approach to unravel strategies deployed by nectarine fruit and during their interaction. We used -inoculated immature and mature fruit, which was resistant and susceptible to brown rot, respectively, to perform a dual RNA-Seq analysis. In immature fruit, host responses, pathogen biomass, and pathogen transcriptional activity peaked at 14-24 h post inoculation (hpi), at which point appeared to switch its transcriptional response to either quiescence or death. Mature fruit experienced an exponential increase in host and pathogen activity beginning at 6 hpi. Functional analyses in both host and pathogen highlighted differences in stage-dependent strategies. For example, in immature fruit, unsuccessfully employed carbohydrate-active enzymes (CAZymes) for penetration, which the fruit was able to combat with tightly regulated hormone responses and an oxidative burst that challenged the pathogen's survival at later time points. In contrast, in mature fruit, was more dependent on proteolytic effectors than CAZymes, and was able to invest in filamentous growth early during the interaction. Hormone analyses of mature fruit infected with indicated that, while jasmonic acid activity was likely useful for defense, high ethylene activity may have promoted susceptibility through the induction of ripening processes. Lastly, we identified genes that were highly induced in both quiescent and active infections and may serve as targets for control of brown rot.
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http://dx.doi.org/10.1038/s41438-020-00387-wDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7527454PMC
October 2020

Scrutinising the relationship between major physiological and compositional changes during 'Merrill O'Henry' peach growth with brown rot susceptibility.

Food Sci Technol Int 2020 Sep 22:1082013220959988. Epub 2020 Sep 22.

Postharvest Department, Institute of Agrifood Research and Technology (IRTA), Edifici Fruitcentre, Parc Científic i Tecnológic Agroalimentari de Lleida, Lleida, Spain.

In the present work, the major physiological and compositional changes occurring during 'Merrill O'Henry' peach growth and its relationship with susceptibility to three strains of spp. at 49, 77, 126 and 160 days after full bloom were explored. Results of disease incidence indicated wide differences among phenological stages, being 49 and 126 days after full bloom the moment when peaches showed significantly lower susceptibility to brown rot (40 and 23% of rotten fruit, respectively, for strain ML8L). Variation in brown rot susceptibility among different growth stages was also strain-dependent. Lower fruit susceptibility to ML8L at 49 and 126 was accompanied by noticeable changes in the fruit ethylene and respiration patterns, and also in sugars and organic acids content. By employing a partial least squares regression model, a strong negative relationship between citric acid, and a positive association of ethylene with peach susceptibility to spp. at diverse phenological stages were observed. The results obtained herein highlight that the content of certain compounds such as citrate, malate and sucrose; the respiratory activity and the fruit ethylene production may mediate in a coordinated manner the fruit resistance to spp. at different phenological stages of peach fruit.
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http://dx.doi.org/10.1177/1082013220959988DOI Listing
September 2020

Ethylene biosynthesis and response factors are differentially modulated during the interaction of peach petals with Monilinia laxa or Monilinia fructicola.

Plant Sci 2020 Oct 13;299:110599. Epub 2020 Jul 13.

XaRTA-Postharvest, Institute of Agrifood Research and Technology (IRTA), Edifici Fruitcentre, Parc Científic i Tecnològic Agroalimentari de Lleida, Parc de Gardeny, 25003 Lleida, Catalonia, Spain. Electronic address:

Monilinia spp. may infect stone fruit at any growth stage, although susceptibility to brown rot depends on both host properties and climatological conditions. This said, no studies deciphering the host response in the interaction between peach blossoms and Monilinia spp. are yet available. This study presents an in-depth characterization of the role of ethylene in the interaction of 'Merrill O'Henry' peach petals (Prunus persica (L.) Batch) with Monilinia laxa and M. fructicola. We investigated the physiological responses of the host and the fungi to the application of ethylene and 1-methylcyclopropene (1-MCP) as well as the molecular patterns associated with the biosynthetic and ethylene-dependent responses during the interaction of both Monilinia species with the host. The incidence of both species was differentially affected by 1-MCP and ethylene; M. laxa was favoured by the enhanced host ethylene production associated with the treatments whereas M. fructicola reduced its infection capacity. Such differences were host-dependent as treatments did not affect growth or colony morphology of Monilinia spp. Besides, host ethylene production was altered in M. laxa inoculated petals, either by the fungus or the host itself. Molecular analysis revealed some important ERFs that could be involved in the different ability of both species to activate a cascade response of peach petals against these pathogens.
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http://dx.doi.org/10.1016/j.plantsci.2020.110599DOI Listing
October 2020

Balance between resilient fruit surface microbial community and population of Monilinia spp. after biopesticide field applications of Penicillium frequentans.

Int J Food Microbiol 2020 Nov 18;333:108788. Epub 2020 Jul 18.

Department of Plant Protection, INIA, Ctra. de La Coruña Km. 7, 28040, Madrid, Spain. Electronic address:

The microbial variability on the host plant surface must be maintained because population diversity and quantity are essential to avoid disease development. It would be necessary to examine the patterns and mechanisms associated with the massive and reiterative introduction of a microbial pest control agent. The effect of inundative releases of biopesticide formulations containing Penicillium frequentans for the control of Monilinia spp. populations, and the effect on fruit surface microbiota on 18 stone fruit field experiments located in four European countries for more than two crop seasons against brown rot were studied. P. frequentans was monitored after application in order to assess whether it was persistent or not in the environment. Hydrolysis of fluorescein diacetate and denaturing gradient gel electrophoresis were used to study the effects of P. frequentans on fungal and bacterial non-target populations on fruit surface. The effect of P. frequentans formulations on the populations of Monilinia spp. on fruit was also assessed in different orchards. P. frequentans population on stone fruit surfaces showed ranged from 100 to 10,000 CFU cm, and postharvest recovered populations were more than 10-100-fold higher than preharvest recovered populations. The population of P. frequentans varied among orchards and years, rather than by the type of formulation. P. frequentans formulation reduced Monilinia spp. population and brown rot and latent infections caused by this pathogen both before and at harvest, while stabilizing or increasing antagonist populations and avoiding non-target microorganisms. However, fungicides reduced significantly the microbial activity on nectarine surfaces.
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http://dx.doi.org/10.1016/j.ijfoodmicro.2020.108788DOI Listing
November 2020

Double-sided battle: The role of ethylene during Monilinia spp. infection in peach at different phenological stages.

Plant Physiol Biochem 2019 Nov 2;144:324-333. Epub 2019 Oct 2.

IRTA, XaRTA-Postharvest, Edifici Fruitcentre, Parc Científic i Tecnològic Agroalimentari de Lleida, Parc de Gardeny, 25003, Lleida, Catalonia, Spain. Electronic address:

Controversy exists on whether ethylene is involved in determining fruit resistance or susceptibility against biotic stress. In this work, the hypothesis that ethylene biosynthesis in peaches at different phenological stages may be modulated by Monilinia spp. was tested. To achieve this, at 49 and 126 d after full bloom (DAFB), ethylene biosynthesis of healthy and infected 'Merryl O'Henry' peaches with three strains of Monilinia spp. (M. fructicola (CPMC6) and M. laxa (CPML11 and ML8L) that differ in terms of aggressiveness) was analysed at the biochemical and molecular level along the course of infection in fruit stored at 20 °C. At 49 DAFB, results evidenced that infected fruit showed inhibition of ethylene production in comparison with non-inoculated fruit, suggesting that the three Monilinia strains were somehow suppressing ethylene biosynthesis to modify fruit defences to successfully infect the host. On the contrary, at 126 DAFB ethylene production increased concomitantly with brown rot spread, and values for non-inoculated fruit were almost undetectable throughout storage at 20 °C. The expression of several target genes involved in the ethylene biosynthetic pathway confirmed that they were differentially expressed upon Monilinia infection, pointing to a strain-dependent regulation. Notably, Prunus persica 1-aminocyclopropane-1-carboxylic acid (ACC) synthase (ACS) (PpACS) family was the most over-expressed over time, demonstrating a positive ethylene regulation, especially at 126 DAFB. At this phenological stage it was demonstrated the ability of Monilinia spp. to alter ethylene biosynthesis through PpACS1 and benefit from the consequences of an ethylene burst likely on cell wall softening. Overall, our results put forward that infection not only among different strains but also at each stage is achieved by different mechanisms, with ethylene being a key factor in determining peach resistance or susceptibility to brown rot.
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http://dx.doi.org/10.1016/j.plaphy.2019.09.048DOI Listing
November 2019

Dispersion, persistence, and stability of the biocontrol agent Penicillium frequentans strain 909 after stone fruit tree applications.

Environ Sci Pollut Res Int 2019 Oct 7;26(28):29138-29156. Epub 2019 Aug 7.

Department of Plant Protection, INIA, Ctra. de La Coruña Km. 7, 28040, Madrid, Spain.

The capacity of dispersion, persistence, and stability from biocontrol agents is essential before these organisms can be developed into a commercial product. Interactions that microorganisms establish with stone fruit trees may be beneficial in the exploitation of trees in agriculture as crop production. The natural background levels of Penicillium frequentans strain 909 dispersion, persistence, and stability were assessed after tree applications and postharvest conditions. A fingerprinting-based approach to trace genetic stability of P. frequentans along stored time and its release in the field was developed. P. frequentans was successfully traced and discriminated. This strain was dispersed well in treated trees, persisting in the ecosystem up to 2 weeks and staying genetically stable after 36 months of storage. However, the dispersal of P. frequentans was very limited on around untreated trees and soil. P. frequentans dispersed randomly into the air, and its presence reduced from the first day to disappear completely at 15-21 days after application. Great losses of P. frequentans and its increased dispersal in open field conditions probably resulted from rainfall. Biological control strategies with Pf909 were discussed.
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http://dx.doi.org/10.1007/s11356-019-06023-yDOI Listing
October 2019

Verifying the biocontrol activity of novel film-forming formulations of Candida sake CPA-1: resilience in relation to environmental factors, rainfall episodes, and control of Botrytis cinerea on different hosts.

J Sci Food Agric 2019 Aug 17;99(11):4969-4976. Epub 2019 Jun 17.

IRTA, XaRTA-Postharvest, Edifici Fruitcentre, Parc Científic i Tecnològic Agroalimentari de Lleida, Lleida, Catalonia, Spain.

Background: The efficacy of Candida sake CPA-1 as a biocontrol agent against several diseases has been studied since it was isolated 20 years ago. However, it was only recently that two suitable and effective film-forming formulations based on potato starch and maltodextrins were developed using the fluidized-bed spray-drying system. The present work aimed to confirm the capability of both novel formulations by testing their resilience on grapes at different temperatures (0, 22, and 30 °C), relative humidities (40% and 85%), and simulated rainfall levels. Another objective was to examine the control of Botrytis cinerea in different hosts.

Results: The CPA-1 cells from both dried formulations survived better than the liquid formulation on grapes stored at 0 and 22 °C regardless of the relative humidity. After simulated rainfall, potato starch formulation achieved significantly higher populations than maltodextrin formulation, although the highest reduction was -1.6 log N N . A positive effect of cell establishment prior to the simulated rainfall was shown, and recovered cells from the potato starch formulation were significantly higher after 72 h of cell establishment. Finally, both formulations reduced the incidence and severity of B. cinerea on pears, apples, and tomatoes.

Conclusion: The potential of these novel film-forming formulations of C. sake CPA-1 was verified. The resilience of formulated C. sake was better than the commercialized liquid formulation, the adherence of the formulations to the grapes improved after an establishment period prior to rain exposure, and the control of B. cinerea was verified in a wider range of hosts. © 2019 Society of Chemical Industry.
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http://dx.doi.org/10.1002/jsfa.9731DOI Listing
August 2019

Exploring sources of resistance to brown rot in an interspecific almond × peach population.

J Sci Food Agric 2019 Jun 20;99(8):4105-4113. Epub 2019 Mar 20.

IRTA, XaRTA-Postharvest, Edifici Fruitcentre, Parc Científic i Tecnològic Agroalimentari de Lleida, Parc de Gardeny, Lleida, Spain.

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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http://dx.doi.org/10.1002/jsfa.9640DOI Listing
June 2019

Novel film-forming formulations of the biocontrol agent Candida sake CPA-1: biocontrol efficacy and performance at field conditions in organic wine grapes.

Pest Manag Sci 2019 Apr 17;75(4):959-968. Epub 2018 Oct 17.

IRTA, XaRTA-Postharvest, Edifici Fruitcentre, Parc Científic i Tecnològic Agroalimentari de Lleida, Lleida, Spain.

Background: The biocontrol agent (BCA) Candida sake CPA-1 has previously effectively reduced Botrytis bunch rot (BBR) and it was also suggested as a promising strategy to control sour rot in grapes under field conditions. However, biocontrol efficacy of solid formulations of CPA-1 has never been tested in field trials. The present study aims to confirm the efficacy against BBR and sour rot in grapes under field conditions of two novel formulations recently developed by the addition of biodegradable coatings using a fluidized-bed spray-drying system.

Results: Novel film-forming formulations of the BCA C. sake CPA-1 controlled B. cinerea as well as liquid formulation. Sour rot control resulted better in the second season and severity reductions were more satisfactory than incidence control. Visual and cryoSEM observations revealed that film-forming treatments were uniformly distributed on plant surfaces. CPA-1 coating could be observed on grapes at harvest time.

Conclusion: The results of this work suggest that solid formulations would be a competitive alternative to conventional fungicides because they were easy to package and transport, and cell viability could be maintained for a long period of time. © 2018 Society of Chemical Industry.
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http://dx.doi.org/10.1002/ps.5200DOI Listing
April 2019

Differential contribution of the two major polygalacturonases from Penicillium digitatum to virulence towards citrus fruit.

Int J Food Microbiol 2018 Oct 31;282:16-23. Epub 2018 May 31.

Instituto de Agroquímica y Tecnología de Alimentos (IATA), Consejo Superior de Investigaciones Científicas (CSIC), Catedrático Agustín Escardino 7, 46980-Paterna, Valencia, Spain. Electronic address:

The fungus Penicillium digitatum is the causal agent of the citrus green mould, the major postharvest diseases of citrus fruit. Lesions on the surface of infected fruits first appear as soft areas around the inoculation site, due to maceration of fruit. The macerating activity has been associated with pectinases secreted by the fungus during infection. In order to evaluate the contribution to virulence and macerating activity of the two major polygalacturonases (PGs) secreted by P. digitatum, we have obtained and characterized mutants lacking either pg1 or pg2, the genes encoding PG1 and PG2, respectively. Disease incidence of deletants in either gene was not different from that of the parental strain or ectopic transformants. However, disease progressed more slowly in deletants, especially in those lacking the pg2 gene. The lesions originated by the Δpg2 deletants were not as soft and the pH was not as acid as those originated by either the wild type strain or the ectopic transformants. Total PG activity in the macerated tissue was also lower in fruits infected with the Δpg2 deletants. Interestingly, the macerated tissue of oranges infected with Δpg2 deletants showed around 50% reduction in galacturonic acid content with respect to lesions caused by any other strain.
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http://dx.doi.org/10.1016/j.ijfoodmicro.2018.05.031DOI Listing
October 2018

Penicillium expansum (compatible) and Penicillium digitatum (non-host) pathogen infection differentially alter ethylene biosynthesis in apple fruit.

Plant Physiol Biochem 2017 Nov 30;120:132-143. Epub 2017 Sep 30.

IRTA, XaRTA-Postharvest, Parc Científic i Tecnològic Agroalimentari de Lleida, Parc de Gardeny, Edifici Fruitcentre, 25003, Lleida, Catalonia, Spain. Electronic address:

The role of ethylene on inducing plant resistance or susceptibility to certain fungal pathogens clearly depends on the plant pathogen interaction with little or no-information available focused on the apple-Penicillium interaction. Taken advantage that Penicillium expansum is the compatible pathogen and P. digitatum is the non-host of apples, the present study aimed at deciphering how each Penicillium spp. could interfere in the fruit ethylene biosynthesis at the biochemical and molecular level. The infection capacity and different aspects related to the ethylene biosynthesis were conducted at different times post-inoculation. The results show that the fruit ethylene biosynthesis was differently altered during the P. expansum infection than in response to other biotic (non-host pathogen P. digitatum) or abiotic stresses (wounding). The first symptoms of the disease due to P. expansum were visible before the initiation of the fruit ethylene climacteric burst. Indeed, the ethylene climacteric burst was reduced in response to P. expansum concomitant to an important induction of MdACO3 gene expression and an inhibition (ca. 3-fold) and overexpression (ca. 2-fold) of ACO (1-Aminocyclopropane-1-carboxylic acid oxidase) and ACS (1-Aminocyclopropane-1-carboxylic acid synthase) enzyme activities, indicating a putative role of MdACO3 in the P. expansum-apple interaction which may, in turn, be related to System-1 ethylene biosynthesis. System-1 is auto-inhibited by ethylene and is characteristic of non-climateric or pre-climacteric fruit. Accordingly, we hypothesise that P. expansum may 'manipulate' the endogenous ethylene biosynthesis in apples, leading to the circumvention or suppression of effective defences hence facilitating its colonization.
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http://dx.doi.org/10.1016/j.plaphy.2017.09.024DOI Listing
November 2017

Fluidised-bed spray-drying formulations of Candida sake CPA-1 by adding biodegradable coatings to enhance their survival under stress conditions.

Appl Microbiol Biotechnol 2017 Nov 23;101(21):7865-7876. Epub 2017 Sep 23.

IRTA, XaRTA-Postharvest, Edifici Fruitcentre, Parc Científic i Tecnològic Agroalimentari de Lleida, 25003, Lleida, Catalonia, Spain.

The biocontrol agent Candida sake CPA-1 has demonstrated to be effective against several diseases on fruit. However, for application of CPA-1 under field conditions, it was necessary to mix it with a food coating to improve survival under stress conditions, as well as adherence and distribution on fruit surfaces. The objective of this study was to obtain a more competitive formulation under field conditions to be applied independently of any product. To achieve this purpose, the drying process of CPA-1 by a fluidised-bed spray-drying system together with biodegradable coatings was optimised. This approach is novel for the drying system used and the formulation obtained which was able to form a film or coating on fruit surfaces. Several substances were tested as carriers and binders, and drying temperature was optimised. The addition of protective compounds was also tested to improve survival of CPA-1 during the dehydration process. Product shelf life, biocontrol efficacy on grapes against Botrytis cinerea, and the improvement of C. sake behaviour under stress conditions were tested. The optimal temperature of drying was 55 °C and two formulations that were able to develop a coating on fruit surfaces were obtained. One of the formulations was created by using a combination of native and pregelatinised potato starch; the other formulation was obtained using maltodextrin and by adding skimmed milk and sucrose as protectant compounds. The formulated products reduced the incidence and severity of B. cinerea, and CPA-1 survival rate was increased under stress conditions of temperature and humidity.
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http://dx.doi.org/10.1007/s00253-017-8529-5DOI Listing
November 2017

Unravelling the contribution of the Penicillium expansum PeSte12 transcription factor to virulence during apple fruit infection.

Food Microbiol 2018 Feb 12;69:123-135. Epub 2017 Aug 12.

IRTA, XaRTA-Postharvest, Parc Científic i Tecnològic Agroalimentari de Lleida, Parc de Gardeny, Edifici Fruit centre, 25003 Lleida, Catalonia, Spain.

Blue mould disease caused by Penicillium expansum infection is one of the most important diseases of pome fruit accounting for important economic losses. In the present study, the PeSte12 transcription factor gene was identified, and deletant mutants were produced by gene replacement. Knockout mutants showed a significant decrease of virulence during apple fruit infection. Virulence was affected by the maturity stage of the fruit (immature, mature and over-mature), and disease severity was notably reduced when the apples were stored at 0 °C. The ΔPeSte12 mutants resulted defective in asexual reproduction, producing less conidia, but this characteristic did not correlate with differences in microscopic morphology. In addition, the ΔPeSte12 mutants produced higher quantity of hydrogen peroxide than the wild type strain. Gene expression analysis revealed that PeSte12 was induced over time during apple infection compared to axenic growth, particularly from 2 dpi, reinforcing its role in virulence. Analysis of transcriptional abundance of several genes in ΔPeSte12 mutants showed that in most of the evaluated genes, PeSte12 seemed to act as a negative regulator during axenic growth, as most of them exhibited an increasing expression pattern along the time period evaluated. The highest expression values corresponded to detoxification, ATPase activity, protein folding and basic metabolism. Gene expression analysis during apple infection showed that 3 out of 9 analysed genes were up regulated; thus, PeSte12 seemed to exert a positive control to particular type of aldolase. These results demonstrate the PeSte12 transcription factor could play an important role in P. expansum's virulence and asexual reproduction.
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http://dx.doi.org/10.1016/j.fm.2017.08.005DOI Listing
February 2018

Environmental fate and behaviour of the biocontrol agent Bacillus amyloliquefaciens CPA-8 after preharvest application to stone fruit.

Pest Manag Sci 2018 Feb 30;74(2):375-383. Epub 2017 Sep 30.

IRTA, XaRTA-Postharvest, Parc Científic i Tecnològic Agroalimentari de Lleida, Parc de Gardeny, Edifici Fruitcentre, Lleida, Spain.

Background: Bacillus amyloliquefaciens strain CPA-8 has been described as an effective biocontrol agent to control brown rot in stone fruit for both preharvest and postharvest applications. However, no information about the environmental fate and behaviour of this strain under field conditions is available.

Results: The dispersion of the CPA-8 application was evaluated using water-sensitive papers, and complete coverage was observed on the leaves of treated trees, while <1% of non-treated tree leaves had CPA-8. CPA-8 persisted on the fruit of treated trees during preharvest and postharvest conditions, while a significant decrease on leaves and weeds was observed 21 days after treatment. On non-treated trees, CPA-8 was detected on leaves until 180 days after treatment, and on weeds, the CPA-8 population was dependent on the distance from the treated trees. A high persistence of CPA-8 was detected on inert materials, such as clothes and gloves worn by handlers and plastic harvesting boxes. More than 99% of the samples with a CPA-8 phenotype were confirmed as CPA-8 using polymerase chain reaction (PCR).

Conclusion: This work demonstrated a good distribution, persistence and adaptation of the CPA-8 strain to field and postharvest conditions. Monitoring of dispersion and persistence is an excellent tool to determine the time of application and provides valuable information for registering issues. © 2017 Society of Chemical Industry.
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http://dx.doi.org/10.1002/ps.4716DOI Listing
February 2018

Biological Characterization of the Biocontrol Agent Bacillus amyloliquefaciens CPA-8: The Effect of Temperature, pH and Water Activity on Growth, Susceptibility to Antibiotics and Detection of Enterotoxic Genes.

Curr Microbiol 2017 Sep 29;74(9):1089-1099. Epub 2017 Jun 29.

IRTA, XaRTA-Postharvest, Edifici Fruitcentre, Parc Científic i Tecnològic Agroalimentari de Lleida, 25003, Lleida, Catalonia, Spain.

This work focuses on the biological understanding of the biocontrol agent Bacillus amyloliquefaciens CPA-8 in order to accomplish the characterization required in the registration process for the development of a microorganism-based product. The tolerance of CPA-8 to grow under different pH-temperature and water activity (a )-temperature conditions was widely demonstrated. Regarding the pH results, optimum growth at the evaluated conditions was observed at 37 °C and pH between 7 and 5. On the contrary, the slowest growth was recorded at 20 °C and pH 4.5. Moreover, the type of solute used to reduce a had a great influence on the minimum a at which the bacterium was able to grow. The lowest a values for CPA-8 growth in media modified with glycerol and glucose were 0.950 and 0.960, respectively. Besides, the lowest a for CPA-8 growth increased when the temperature decreased to 20 °C, at which CPA-8 was not able to grow at less than 0.990 a , regardless of the type of solute. Antibiotic susceptibility tests were carried out to determine which antibiotic could affect the behavior of the bacteria and revealed that CPA-8 was clearly resistant to hygromycin. Finally, a PCR amplification assay to detect the presence of enterotoxic genes from Bacillus cereus in CPA-8 was also performed. CPA-8 gave negative results for all the genes tested except for nheA gene, which is not enough for the toxicity expression, suggesting that fruit treated with this antagonist will not be a potential vehicle for foodborne illnesses.
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http://dx.doi.org/10.1007/s00284-017-1289-8DOI Listing
September 2017

Relevance of the main postharvest handling operations on the development of brown rot disease on stone fruits.

J Sci Food Agric 2017 Dec 28;97(15):5319-5326. Epub 2017 Jun 28.

IRTA, XaRTA-Postharvest, Edifici Fruitcentre, Parc Científic i Tecnològic Agroalimentari de Lleida, Lleida, Catalonia, Spain.

Background: Brown rot caused by Monilinia spp. is one of the most important postharvest diseases of stone fruit. The aim of this study was to evaluate the relevance of the main postharvest operations of fruit - hydrocooling, cold room, water dump, sorting and cooling tunnel - in the development of M. laxa on peaches and nectarines artificially infected 48, 24 or 2 h before postharvest operations.

Results: Commercial hydrocooling operation reduced incidence to 10% in 'Pp 100' nectarine inoculated 2 and 24 h before this operation; however, in 'Fantasia' nectarine incidence was not reduced, although lesion diameter was decreased in all studied varieties. Hydrocooling operation for 10 min and 40 mg L of sodium hypochlorite reduced brown rot incidence by 50-77% in nectarines inoculated 2 h before operation; however, in peach varieties it was not reduced. Water dump operation showed reduction of incidence on nectarine infected 2 h before immersion for 30 s in clean water at 4 °C and 40 mg L sodium hypochlorite; however, in peach varieties it was not reduced. Cold room, sorting and cooling tunnel operation did not reduce brown rot incidence.

Conclusion: From all studied handling operations on stone fruit packing houses, hydrocooling is the most relevant in the development of brown rot disease. Duration of the treatment seems to be more important than chlorine concentration. In addition, hydrocooling and water dump were less relevant in peaches than in nectarines. As a general trend, hydrocooling and water dump reduced incidence on fruit with recent infections (2 or 24 h before operation); however, when infections have been established (48 h before operation) diseases were not reduced. © 2017 Society of Chemical Industry.
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http://dx.doi.org/10.1002/jsfa.8419DOI Listing
December 2017

Dry formulations of the biocontrol agent Candida sake CPA-1 using fluidised bed drying to control the main postharvest diseases on fruits.

J Sci Food Agric 2017 Aug 23;97(11):3691-3698. Epub 2017 Feb 23.

IRTA, XaRTA-Postharvest, Edifici Fruitcentre, Parc Científic i Tecnològic Agroalimentari de Lleida, Lleida, Catalonia, Spain.

Background: The biocontrol agent Candida sake CPA-1 is effective against several diseases. Consequently, the optimisation of a dry formulation of C. sake to improve its shelf life and manipulability is essential for increasing its potential with respect to future commercial applications. The present study aimed to optimise the conditions for making a dry formulation of C. sake using a fluidised bed drying system and then to determine the shelf life of the optimised formulation and its efficacy against Penicillium expansum on apples.

Results: The optimal conditions for the drying process were found to be 40 °C for 45 min and the use of potato starch as the carrier significantly enhanced the viability. However, none of the protective compounds tested increased the viability of the dried cells. A temperature of 25 °C for 10 min in phosphate buffer was considered as the optimum condition to recover the dried formulations. The dried formulations should be stored at 4 °C and air-packaged; moreover, shelf life assays indicated good results after 12 months of storage. The formulated products maintained their biocontrol efficacy.

Conclusion: A fluidised bed drying system is a suitable process for dehydrating C. sake cells; moreover, the C. sake formulation is easy to pack, store and transport, and is a cost-effective process. © 2017 Society of Chemical Industry.
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http://dx.doi.org/10.1002/jsfa.8229DOI Listing
August 2017

Relevance of the transcription factor PdSte12 in Penicillium digitatum conidiation and virulence during citrus fruit infection.

Int J Food Microbiol 2016 Oct 22;235:93-102. Epub 2016 Jul 22.

Laboratorio de Micología, Centro de Protección Vegetal y Biotecnología, Instituto Valenciano de Investigaciones Agrarias (IVIA), Apartado Oficial. 46113- Moncada, Valencia, Spain. Electronic address:

Green mould, resulting from Penicillium digitatum, is the most important postharvest disease of citrus. In a previous study, the PdSte12 transcription factor gene was identified, and disruption mutants were obtained. In the present study, the ΔPdSte12 mutants generated through gene replacement showed significantly reduced virulence during citrus fruit infection. Virulence was affected not only in mature fruit but also in immature fruit, and disease severity was markedly reduced when the oranges were stored at 20 or 4°C. In addition, the ΔPdSte12 mutants were defective in asexual reproduction, producing few conidia. The conidiophores of these mutants had longer metulae with fewer branches at the tip of the hyphae. Gene expression analysis revealed that PdSte12 might act as a negative regulator of several transporter-encoding genes and a positive regulator of two sterol demethylases, all of which are involved in fungicide resistance and fungal virulence. Moreover, PdSte12 exhibited the negative regulation of another transcription factor PdMut3, putatively involved in fungal pathogenesis but with no effect on the MAPK SLT2 P. digitatum orthologue belonging to different transcription pathways relevant to cell integrity. These results indicate the PdSte12 transcription factor is functionally conserved in P. digitatum for infection and asexual reproduction, similar to other Ste12 fungal plant pathogens.
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http://dx.doi.org/10.1016/j.ijfoodmicro.2016.07.027DOI Listing
October 2016

DNA-based methodologies for the quantification of live and dead cells in formulated biocontrol products based on Pantoea agglomerans CPA-2.

Int J Food Microbiol 2015 Oct 20;210:79-83. Epub 2015 Jun 20.

IRTA, XaRTA-Postharvest, Edifici Fruitcentre, Parc Científic i Tecnològic Agroalimentari de Lleida, Parc de Gardeny, 25003 Lleida, Catalonia, Spain. Electronic address:

Pantoea agglomerans strain CPA-2 is an effective biocontrol agent (BCA) against the major postharvest pathogens present on pome and citrus fruits. Dehydration, such as freeze-drying, spray-drying and fluidized bed drying is one of the best ways to formulate BCAs. In this work, the survival of CPA-2 cells after formulation was determined by dilution plating and molecular methods as qPCR alone and combined with a sample pretreatment with a propidium monoazide dye (PMA-qPCR) and they were used to calculate treatment concentrations in efficacy trials on postharvest oranges. Furthermore, no significant differences in CPA-2 survival were observed as determined by dilution plating and PMA-qPCR after both the freeze drying and fluidized bed drying processes; however, an interesting significant difference was observed in the spray dried product comparing all quantitative methods. A difference of 0.48 and 2.17 log10 CFU or cells g/dw was observed among PMA-qPCR with qPCR and dilution plating, respectively. According to our study, dilution plating was shown to be an unreliable tool for monitoring the survival of CPA-2 after spray drying. In contrast, the combination of PMA and qPCR enabled a quick and unequivocal methodology to enumerate viable and VBNC CPA-2 cells under stress-dried conditions. Efficacy trials showed that, after 3 days, spray drying formulation rehydrated with 10% non-fat skimmed milk (NFSM) was as effective as fresh cells to control Penicillium digitatum in oranges.
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http://dx.doi.org/10.1016/j.ijfoodmicro.2015.06.013DOI Listing
October 2015

Characterizing the proteome and oxi-proteome of apple in response to a host (Penicillium expansum) and a non-host (Penicillium digitatum) pathogen.

J Proteomics 2015 Jan 20;114:136-51. Epub 2014 Nov 20.

IRTA, XaRTA-Postharvest, Rovira Roure 191, 25198 Lleida, Catalonia, Spain. Electronic address:

Unlabelled: Apples are subjected to both abiotic and biotic stresses during the postharvest period, which lead to large economic losses worldwide. To obtain biochemical insights into apple defense response, we monitored the protein abundance changes (proteome), as well as the protein carbonyls (oxi-proteome) formed by reactive oxygen species (ROS) in 'Golden Smoothee' apple in response to wounding, Penicillium expansum (host) and Penicillium digitatum (non-host) pathogens with select transcriptional studies. To examine the biological relevance of the results, we described quantitative and oxidative protein changes into the gene ontology functional categories, as well as into de KEGG pathways. We identified 26 proteins that differentially changed in abundance in response to wounding, P. expansum or P. digitatum infection. While these changes showed some similarities between the apple responses and abiotic and biotic stresses, Mal d 1.03A case, other proteins as Mal d 1.03E and EF-Tu were specifically induced in response to P. digitatum infection. Using a protein carbonyl detection method based on fluorescent Bodipy, we detected and identified 27 oxidized proteins as sensitive ROS targets. These ROS target proteins were related to metabolism processes, suggesting that this process plays a leading role in apple fruit defense response against abiotic and biotic stresses. ACC oxidase and two glutamine synthetases showed the highest protein oxidation level in response to P. digitatum infection. Documenting changes in the proteome and, specifically in oxi-proteome of apple can provide information that can be used to better understand how impaired protein functions may affect apple defense mechanisms. Possible mechanisms by which these modified proteins are involved in fruit defense response are discussed.

Biological Significance: Mechanical damage in apple fruits is linked annually to large economic losses due to opportunistic infection by postharvest pathogens, such as P. expansum. Despite the current use of chemical fungicides and the implementation of new alternative strategies, blue mold remains a critical disease of these stored fruits worldwide. Actual trends are focused on acquiring the knowledge of the host-pathogen interactions because it may help on finding new rational and environmentally friendly control alternatives. Despite the economic importance of some postharvest diseases, proteomics has only been applied in a few cases to study fruit-pathogen interactions. On the one hand, this is the first study that monitored changes at the proteome and oxi-proteome level in 'Golden Smoothee' apple fruits in response to P. expansum (compatible) and P. digitatum (non-host) pathogens. On the other hand, the main technological innovation of the reported research is the detection and quantification of oxidized (carbonylated) proteins to assess protein oxidative damage, avoiding the immunoblotting technique. The importance of the biological process investigated lies in the different mechanisms induced in fruit in response to P. expansum and P. digitatum. Results revealed that fruit recognizes and reacts to P. expansum in a similar manner to wounding, while its response to P. digitatum exhibits few differences in the protein profile. Documenting changes in the proteome and, specifically in oxi-proteome of apple can provide information that can be used to better understand how impaired protein functions may affect apple defense mechanisms. It also provides new biomarkers for oxidative damage mainly caused by the oxidative response occurring in fruit tissue in response to a host and a non-host pathogen.
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http://dx.doi.org/10.1016/j.jprot.2014.11.007DOI Listing
January 2015

Development of PMA real-time PCR method to quantify viable cells of Pantoea agglomerans CPA-2, an antagonist to control the major postharvest diseases on oranges.

Int J Food Microbiol 2014 Jun 13;180:49-55. Epub 2014 Apr 13.

IRTA, XaRTA-Postharvest, Edifici Fruitcentre, Parc Científic i Tecnològic Agroalimentari de Lleida, Parc de Gardeny, 25003 Lleida Catalonia, Spain. Electronic address:

Dilution plating is the quantification method commonly used to estimate the population level of postharvest biocontrol agents, but this method does not permit a distinction among introduced and indigenous strains. Recently, molecular techniques based on DNA amplification such as quantitative real-time PCR (qPCR) have been successfully applied for their high strain-specific detection level. However, the ability of qPCR to distinguish viable and nonviable cells is limited. A promising strategy to avoid this issue relies on the use of nucleic acid intercalating dyes, such as propidium monoazide (PMA), as a sample pretreatment prior to the qPCR. The objective of this study was to optimize a protocol based on PMA pre-treatment samples combined with qPCR to distinguish and quantify viable cells of the biocontrol agent P. agglomerans CPA-2 applied as a postharvest treatment on orange. The efficiency of PMA-qPCR method under the established conditions (30μM PMA for 20min of incubation followed by 30min of LED light exposure) was evaluated on an orange matrix. Results showed no difference in CFU or cells counts of viable cells between PMA-qPCR and dilution plating. Samples of orange matrix inoculated with a mixture of viable/dead cells showed 5.59log10 CFU/ml by dilution plating, 8.25log10 cells/ml by qPCR, and 5.93log10 cells/ml by PMA-qPCR. Furthermore, samples inoculated with heat-killed cells were not detected by dilution plating and PMA-qPCR, while by qPCR was of 8.16log10 cells/ml. The difference in quantification cycles (Cq) among qPCR and PMA-qPCR was approximately 16cycles, which means a reduction of 65,536 fold of the dead cells detected. In conclusion, PMA-qPCR method is a suitable tool for quantify viable CPA-2 cells, which could be useful to estimate the ability of this antagonist to colonize the orange surface.
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http://dx.doi.org/10.1016/j.ijfoodmicro.2014.04.011DOI Listing
June 2014

Detection and quantification by PCR assay of the biocontrol agent Pantoea agglomerans CPA-2 on apples.

Int J Food Microbiol 2014 Apr 31;175:45-52. Epub 2014 Jan 31.

IRTA, Postharvest XaRTA, Av. Rovira Roure, 191, 25198 Lleida, Catalonia, Spain. Electronic address:

The registration of biological control agents requires the development of monitoring systems to detect and quantify the agent in the environment. Pantoea agglomerans CPA-2 is an effective biocontrol agent for postharvest diseases of citrus and pome fruits. The monitoring of CPA-2 in postharvest semi-commercial trials was evaluated by Rodac impression plates and the colonies isolated were confirmed by conventional PCR using the SCAR primers PAGA1 and PAGB1. Samples were taken from different surfaces that had contact with CPA-2, the surrounding environment and working clothes worn by handlers. Moreover, population dynamics of the strain CPA-2 were determined on apple surfaces using both the classical plating technique and real-time quantitative PCR (qPCR). A qPCR assay using a 3'-minor groove-binding (MGB) probe was developed for the specific detection and quantification of P. agglomerans strain CPA-2. Based on the nucleotide sequence of a SCAR fragment of CPA-2, one primer set and TaqMan MGB probe were designed. The primers SP2-F/SP2-R and the TaqMan MGB probe showed a specific detection of strain CPA-2 on apple surfaces, which was verified tested against purified DNA from 17 strains of P. agglomerans, 4 related Pantoea species, and 21 bacterial strains from other genera isolated from whole and also freshly-cut fruit and vegetables. The detection level was approximately 10(3) cells per reaction, and the standard curve was linear within a range of 5log units. Results from semi-commercial trials showed that CPA-2 had a low impact. The maximum persistence of P. agglomerans CPA-2 was not longer than 5days in plastic boxes stored at 0°C. Significant differences in CPA-2 population level dynamics were observed in results obtained by qPCR and dilution plating. These differences may indicate the presence of non-degraded DNA from non-viable cells. In conclusion, qPCR is a novel potential tool to quickly and specifically monitor recent surface colonisation by CPA-2 populations on apple surfaces during large-scale experiments that could ensure efficient and successful treatments.
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http://dx.doi.org/10.1016/j.ijfoodmicro.2014.01.014DOI Listing
April 2014

Potential secondary inoculum sources of Botrytis cinerea and their influence on bunch rot development in dry Mediterranean climate vineyards.

Pest Manag Sci 2014 Jun 2;70(6):922-30. Epub 2013 Oct 2.

Food Technology Department, Lleida University, XaRTA-Postharvest, Agrotecnio Center, Lleida, Catalonia, Spain.

Background: Epidemiological studies have described the life cycle of B. cinerea in vineyards. However, there is a lack of information on the several infection pathways and the quantitative relationships between secondary inoculum and bunch rot at harvest.

Results: Over two seasons, different spray programmes were used to determine key phenological stages for bunch rot development. Secondary inoculum sources within the bunch were also studied. The relative importance of flowering was evidenced in the given conditions, as treatments that included two fungicide applications at flowering were the most effective. In 2010, under conducive meteorological conditions for B. cinerea development after veraison, an extra application provided significantly higher control. Infections of necrotic tissues inside the bunch and latent infections developed mainly during flowering, while very low quantities of B. cinerea conidia were recovered from the fruit surface at veraison. Regression analysis correlated the incidence of latent infections and B. cinerea incidence on calyptras and aborted fruits at veraison with incidence of Botrytis bunch rot at harvest, presenting R2 = 0.95 for the overall regression model.

Conclusion: This work points out key phenological stages during the season for bunch rot and B. cinerea secondary inoculum development and relates quantitatively inoculum sources at veraison to bunch rot at harvest. Recommendations for field applications of antibotrytic products are also suggested.
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http://dx.doi.org/10.1002/ps.3629DOI Listing
June 2014

Suppression of Botrytis cinerea on necrotic grapevine tissues by early-season applications of natural products and biological control agents.

Pest Manag Sci 2014 Apr 1;70(4):595-602. Epub 2013 Jul 1.

Food Technology Department, Lleida University, XaRTA-Postharvest, Agrotecnio Center, Lleida, Catalonia, Spain.

Background: Necrotic tissues within grape (Vitis vinifera) bunches represent an important source of Botrytis cinerea inoculum for Botrytis bunch rot (BBR) at harvest in vineyards. This research quantified the incidence of B. cinerea on necrotic floral and fruit tissues and the efficacy of biologically based treatments for suppression of B. cinerea secondary inoculum within developing bunches.

Results: At veraison (2009 and 2010), samples of aborted flowers, aborted fruits and calyptras were collected, and the incidence and sporulation of B. cinerea were determined. Aborted fruits presented significantly higher incidence in untreated samples. Early-season applications of Candida sake plus Fungicover®, Fungicover alone or Ulocladium oudemansii significantly reduced B. cinerea incidence on aborted flowers and calyptras by 46-85%. Chitosan treatment significantly reduced B. cinerea incidence on calyptras. None of the treatments reduced B. cinerea incidence on aborted fruits. Treatments significantly reduced sporulation severity by 48% or more.

Conclusions: Treatments were effective at reducing B. cinerea secondary inoculum on necrotic tissues, in spite of the variable control on aborted fruits. This is the first report to quantify B. cinerea on several tissues of bunch trash and to describe the effective suppression of saprophytic B. cinerea inoculum by biologically based treatments.
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http://dx.doi.org/10.1002/ps.3587DOI Listing
April 2014

Control of foodborne pathogens on fresh-cut fruit by a novel strain of Pseudomonas graminis.

Food Microbiol 2013 Jun 31;34(2):390-9. Epub 2013 Jan 31.

Food Technology Department, Lleida University, XaRTA-Postharvest, Agrotecnio Center, Rovira Roure 191, 25198 Lleida, Catalonia, Spain.

The consumption of fresh-cut fruit has substantially risen over the last few years, leading to an increase in the number of outbreaks associated with fruit. Moreover, consumers are currently demanding wholesome, fresh-like, safe foods without added chemicals. As a response, the aim of this study was to determine if the naturally occurring microorganisms on fruit are "competitive with" or "antagonistic to" potentially encountered pathogens. Of the 97 and 107 isolates tested by co-inoculation with Escherichia coli O157:H7, Salmonella and Listeria innocua on fresh-cut apple and peach, respectively, and stored at 20 °C, seven showed a strong antagonistic capacity (more than 1-log unit reduction). One of the isolates, CPA-7, achieved the best reduction values (from 2.8 to 5.9-log units) and was the only isolate able to inhibit E. coli O157:H7 at refrigeration temperatures on both fruits. Therefore, CPA-7 was selected for further assays. Dose-response assays showed that CPA-7 should be present in at least the same amount as the pathogen to adequately reduce the numbers of the pathogen. From the results obtained in in vitro assays, competition seemed to be CPA-7's mode of action against E. coli O157:H7. The CPA-7 strain was identified as Pseudomonas graminis. Thus, the results support the potential use of CPA-7 as a bioprotective agent against foodborne pathogens in minimally processed fruit.
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http://dx.doi.org/10.1016/j.fm.2013.01.013DOI Listing
June 2013

Liquid Formulation of the Postharvest Biocontrol Agent Candida sake CPA-1 in Isotonic Solutions.

Phytopathology 2003 Apr;93(4):436-42

ABSTRACT Viability of the postharvest biocontrol agent Candida sake CPA-1 stored as liquid formulation was evaluated by studying the effect of growth, preservation medium, and temperature. C. sake was grown in molasses medium with unmodified water activity (a(w)) and in the same with a(w) modified to 0.98 with the addition of several solutes. Cells were preserved with isotonic solutions of different substances. Efficacy of liquid formulations stored for different periods was tested against infection by Penicillium expansum on apples. The best growth media were the (unmodified one and those modified to 0.98 a(w) with the addition of glycerol or sorbitol. For all growth media, the best preservation medium was the isotonic solution prepared with trehalose. When the effect of trehalose concentration in the preservation medium was studied, generally, at trehalose concentrations below the isotonic one, C. sake viabilities increased with increased trehalose. However, the best results were obtained when cells were preserved with the trehalose solution which was isotonic with cells. After 7 months of storage at 4 degrees C, cells that were grown in the sorbitol-modified medium and preserved with the isotonic solution of trehalose (0.96 M) maintained their viability and efficacy against P. expansum infection of apples.
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http://dx.doi.org/10.1094/PHYTO.2003.93.4.436DOI Listing
April 2003

Improved Control of Postharvest Decay of Pears by the Combination of Candida sake (CPA-1) and Ammonium Molybdate.

Phytopathology 2002 Mar;92(3):281-7

ABSTRACT The potential enhancement of Candida sake (CPA-1) by ammonium molybdate to control blue and gray mold caused by Penicillium expansum and Botrytis cinerea, respectively, on Blanquilla pears was investigated. In laboratory trials, improved control of blue and gray molds was obtained with the application of ammonium molybdate (1, 5, 10, and 15 mM) alone or in combination with C. sake at 2 x 10(6) or 2 x 10(7) CFU ml(-1) on Blanquilla pears stored at 20 degrees C. In semicommercial trials at 1 degrees C for 5 months, the efficacy of C. sake at 2 x 10(6) CFU ml(-1) on reducing P. expansum and B. cinerea decay was enhanced more than 88% with the addition of ammonium molybdate 5 mM in the 1999-2000 season. In two seasons, the performance C. sake at 2 x 10(6) CFU ml(-1) plus ammonium molybdate was similar to or greater than that of C. sake at 2 x 10(7) CFU ml(-1). Similar control of blue mold was obtained on pears stored under low oxygen conditions. The preharvest application of ammonium molybdate did not reduce postharvest blue mold decay. The population of C. sake on pear wounds significantly decreased in the presence of ammonium molybdate 1 and 5 mM at 20 and 1 degrees C.
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http://dx.doi.org/10.1094/PHYTO.2002.92.3.281DOI Listing
March 2002