Aureobasidium pullulans strain Ach1-1 a biocontrol of postharvest diseases of apples: 15 crucial years of research before starting commercial development

Losses in harvested fruits are thoroughly associated to decaying fungi. Biological control using microbial agents including yeasts, has been reported among several alternatives to the use of synthetic chemical fungicides for managing postharvest fruit decay. Aureobasidium pullulans strain Ach1-1was isolated as potential yeast antagonist form the surface of Golden Delicious apple fruit. The biocontrol agent exhibit high efficacy towards controlling blue and grey mold infection disease caused respectively by the two fungi P. expansum and Botrytis cinerea. Competition for nutrients was evident for strain Ach1-1 against P. expansum. The results demonstrated that exogenous amino acids, applied at high concentrations on apple wounds as a mixture of specific amino acid groups or as individuals, significantly decreased strain Ach1-1 efficacy towards P. expansum. In addition molecular markers and a semi-selective medium methods were developed, in order to monitor the population dynamic of A. pullulans strain Ach1-1 on fruit surface. The random amplified polymorphic DNA (RAPD) technique was applied to 15 strains of A. pullulans, including the strain Ach1-1. Among the five specific RAPD fragments amplified for strain Ach1-1, a 528 bp fragment was selected and used to design sequence-characterized amplified region (SCAR) primers. The results showed that these specific SCAR primers can clearly identify strain Ach1-1 among different strains of A. pullulans and other yeast strains commonly present on apple fruit surface. Furthermore, a semi-selective medium based PDA and supplemented with euparen, sumico, hygromycin B, streptomycin sulphate, cycloheximide, specific for strain Ach1-1 was developed. These outcomes in fundamental and applied research, relevant for Aureobasidium pullulans strain Ach1-1 lead to a collaboration establishment with Elephant vert group towards the commercial development of this strain as potential biocontrol agent to control apple diseases in postharvest conditions.Développement d’une formulation de biocontrôle à base d’Aureobasidium pullulans Ach1.1 contre des pathogènes de cultures maraîchère et fruitières en pré et post-récolt

Aureobasidium pullulans strain Ach1-1 a potential biocontrol agent of postharvest diseases of apples

Aureobasidium pullulans strain Ach1-1was isolated form the surface of Golden Delicious apple fruit. The strain Ach1-1 was tested for their efficiency against variable strains of P. expansum the causal agent of bleu mold infection disease of apples in postharvest conditions. The efficacy of strain Ach1-1 was monitored on time along a period of 5, 7 and 10 days storage at 25°C and one to six months storage at 4°C. The ability of Ach1-1 to control P. expansum infection was evaluated through disease incidence (%) and severity (lesion diameter cm) the results showed that strain Ach1-1 display high efficacy to control bleu mold infection disease compared to chemical fungicide and Boniprotect., and sustain this efficiency along a storage period of 4 months at 4°C. Which make it a well-placed Biocontrol agent to manage post-harvest disease of apples. Besides, the industrial production of the yeast strains was carried out using the Fed Batch technology and freeze drying process. The efficacy of the produced strain was investigated, and results showed lower biocontrol efficiency than the active yeast. Hence a downstream formulation trials were carried out in an attempt to enhance the efficacy of produced yeast using amino acids, salts, and polyols. The results showed that the application of some adjuvants individually may enhance the efficiency of the yeast applied at low concentrationDéveloppement d’une formulation de biocontrôle à base d’Aureobasidium pullulans Ach1.1 contre des pathogènes de cultures maraîchère et fruitières en pré et post-récolt

Characterization of Volatiles Organics compounds of two biocontrol agents Pichia anomala strain K and Candida oelophila strain O

Among the large diversity of microbial secondary metabolites, low molecular-weight volatile organic compounds (VOCs) have received growing attention in the past decade. Many fungal species and yeast have the ability to produce low concentrations of antifungal substances. This would open the way as alternative method to control microbial decays via biofumigation, as it does not require physical contact with the product or commodity to be treated. The yeasts antagonists, Pichia anomala strain K, and Candida oelophila Strain O were among the most studied yeast antagonists in Phytopathology Lab. And well known as potential biocontrol agent to manage post-harvest disease of apples. Beyond their primary mode of action, which rely on nutrient competition and glucanase production, the ability of these yeasts to produce volatiles organic compounds was investigated. The VOCs were assayed with a double petri dish test against P. expansum and B. cinerea. Results showed that the VOCs generated by the antagonists inhibited significantly pathogen growth. In parallel an in vivo trial was carried out to assess the ability of produced VOCs to inhibit pathogen growth in in vivo conditions. The characterization of produced volatiles was assessed using solid-phase microextraction (SPME)–gas chromatographic technique. The results showed a three common produced compounds: the 1-Propanol, 2-methyl, Isoamylalcohol and the phenethyl alcohol. The pure standard compounds were tested individually to assess their ability in pathogen growth inhibition

Aureobasidium pullulans strain Ach1-1 in biocontrol of postharvest diseases of apples: 15 crucial years of research before starting commercial development

Significant losses in harvested fruits are directly attributable to decaying fungi. Biological control using microbial agents including yeasts has been reported among several alternatives to the use of synthetic chemical fungicides for managing postharvest fruit decay. Economic losses caused by postharvest diseases represent one of the main problems of the apple industry worldwide. The major diseases affecting citrus are the "green mold" and "blue mold", caused by Penicillium digitatum and P. italicum, respectively. To control them, synthetic fungicides are the most commonly used method. However, often the emergence of resistant strains occurs and their use is becoming more restricted because of toxic effects and environmental pollution they generate, combined with trade barriers to international markets. The aim of this work was to isolate indigenous killer yeasts Postharvest fungal pathogens are considered the main cause of fresh fruits losses in storage conditions. As a countermeasure yeasts showed to be potential candidates for an efficient biocontrol of postharvest pathogens since they colonize efficiently and steadily wounded and non-wounded plant surfaces even under unfavourable conditions. The aim This led us to select in vivo a potential yeast biocontrol agent able to protect apple fruits in particular, against the fungi Penicillium expansum and Botrytis cinerea in postharvest conditions. The yeast antagonist isolated form the surface of Golden Delicious apple fruit and characterized as Aureobasidium pullulans strain Ach1-1, showed significant ability in controlling blue and grey mold infection diseases. Efficacy results revealed that A. pullulans strain Ach1-1 allowed high protection level (85%) against the two tested pathogens at 25°C and in storage conditions [1]. Many challenges needs to be addressed in order to develop a successful postharvest Biocontrol Agent. From a commercial point of view, a deep understanding of the action mode is essential to develop appropriate formulation, methods of application, and to obtain registration. In this regard, the possible involvement of competition for nutrients in the biocontrol activity of this strain both in vitro and in situ was investigated. The results showed evidence that competition for apple nutrients mainly amino acids and especially Serine, reflects the potential mechanism of strain Ach1-1 biocontrol activity against blue mold infection disease [2]. Special emphasis will be taken to these results. Their implication on the formulation will be further presented. Besides, in an attempt to monitor the population dynamic of A. pullulans strain X on fruit surface, molecular markers and a semi-selective medium method were developed. The random amplified polymorphic DNA (RAPD) technique was applied to a collection of 15 strains of A. pullulans, including the strain Ach1-1. Five specific RAPD fragments were amplified for strain Ach1-1, among them, a fragment of 528 bp specific to this strain was selected, cloned, sequenced, and used to design sequence-characterized amplified region (SCAR) primers. The results showed that the SCAR primers can clearly identify strains Ach1-1 among 14 strains of A. pullulans and among eight yeast strains commonly present on apple fruit surfaces. In addition a semi-selective medium, PDA medium supplemented with euparen, sumico, hygromycin B, streptomycin sulphate, cycloheximide, was developed. These two methods displayed sufficient and high accuracy to monitor strain Ach1-1 populations [3]. Finally, a first trial of biomass production, formulation and evaluation of the formulated yeast for its antagonistic activity at pilot scale was conducted. The results showed high protection level achieved with the formulated A. pullulans strain Ach1-1 towards controlling apple decay caused by Penicillium expansum after 28 and 7 days stored respectively at 5 and 25°C [4]. Based on these crucial steps, Aureobasidium pullulans strain Ach1-1 gained a step stone in fundamental and applied research, leading to a collaboration establishment with Elephant vert group towards its commercial development as potential biocontrol agent for postharvest apple diseases.Développement d’une formulation de biocontrôle à base d’Aureobasidium pullulans Ach1.1 contre des pathogènes de cultures maraîchère et fruitières en pré et post-récolt

Trade-Off between Growth and Carbohydrate Accumulation in Nutrient-Limited Arthrospira sp PCC 8005 Studied by Integrating Transcriptomic and Proteomic Approaches

Cyanobacteria have a strong potential for biofuel production due to their ability to accumulate large amounts of carbohydrates. Nitrogen (N) stress can be used to increase the content of carbohydrates in the biomass, but it is expected to reduce biomass productivity. To study this trade-off between carbohydrate accumulation and biomass productivity, we characterized the biomass productivity, biomass composition as well as the transcriptome and proteome of the cyanobacterium Arthrospira sp. PCC 8005 cultured under N-limiting and N-replete conditions. N limitation resulted in a large increase in the carbohydrate content of the biomass (from 14 to 74%) and a decrease in the protein content (from 37 to 10%). Analyses of fatty acids indicated that no lipids were accumulated under N-limited conditions. Nevertheless, it did not affect the biomass productivity of the culture up to five days after N was depleted from the culture medium. Transcriptomic and proteomic analysis indicated that de novo protein synthesis was down-regulated in the N-limited culture. Proteins were degraded and partly converted into carbohydrates through gluconeogenesis. Cellular N derived from protein degradation was recycled through the TCA and GS-GOGAT cycles. In addition, photosynthetic energy production and carbon fixation were both down-regulated, while glycogen synthesis was up-regulated. Our results suggested that N limitation resulted in a redirection of photosynthetic energy from protein synthesis to glycogen synthesis. The fact that glycogen synthesis has a lower energy demand than protein synthesis might explain why Arthrospira is able to achieve a similar biomass productivity under N-limited as under N-replete conditions despite the fact that photosynthetic energy production was impaired by N limitation.status: publishe

Characterization of Aureobasidium pullulans Isolates Selected as Biocontrol Agents Against Fruit Decay Pathogens

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