Postharvest Fruit Decay Research Articles

Enhancement of Biocontrol Efficacy of Pichia kudriavzevii Induced by Ca Ascorbate against Botrytis cinerea in Cherry Tomato Fruit and the Possible Mechanisms of Action

ABSTRACTThis study investigated the effect of Ca ascorbate on the biocontrol efficacy of Pichia kudriavzevii and the possible mechanisms. The results indicated that the biocontrol activity of P. kudriavzevii was significantly enhanced by 0.15 g L−1 of Ca ascorbate, with higher growth rates of yeast cells in vitro and in vivo. The antioxidant enzyme activity in P. kudriavzevii, including catalase (CAT), superoxide dismutase (SOD), and peroxidase (POD), were improved by Ca ascorbate and reached the maximum at 96 h, 96 h, and 72 h, respectively. The expression of the antioxidant enzyme-related genes CAT1 (8.55-fold) and SOD2 (7.26-fold) peaked at 96 h, while PRXIID (2.8-fold) peaked at 48 h, which were similar to the trends of enzyme activities. Compared with the control, 0.15 g L−1 of Ca ascorbate and CaCl2 increased the activity of succinate dehydrogenase in P. kudriavzevii, thereby enhancing the utilization of nutrients by yeast cells, and calcium ascorbate had the strongest effect. The expressions of HXT5, ADH6, PET100p, and Pga62 were significantly higher in the Ca ascorbate treatment than the other groups, and the CaCl2 treatment was also significantly higher than the control. These results indicated that Ca ascorbate can effectively improve the energy metabolism and cell wall synthesis and slow down the senescence of yeast cells. In general, Ca ascorbate can improve the environmental adaptability of P. kudriavzevii and thus improve the biocontrol effect, which is associated with inducing antioxidant enzymes in yeast cells and enhancing energy metabolism and nutrient utilization efficiency to increase nutrient competition with pathogens.IMPORTANCE Antagonistic yeast is a promising way to control postharvest fruit decay because of its safety and broad-spectrum resistance. However, the biocontrol efficacy of yeast is limited by environmental stress, such as oxidative stress. Therefore, the improvement of antioxidant capacity has become a research hot spot in improving the biocontrol efficacy of yeast. The induction of Ca ascorbate on the antioxidant capacity and physiological activity of yeast was studied. The results showed better induction of antioxidant enzyme and physiological activity in yeast by Ca ascorbate for better antioxidant capacity, and Ca2+ also played a synergistic promotion effect, which improved the biocontrol efficacy. These results provide an approach for the research and application of improving the environmental adaptability and biocontrol effectiveness of yeast.

Genomic prediction of strawberry resistance to postharvest fruit decay caused by the fungal pathogen Botrytis cinerea.

Gray mold, a disease of strawberry (Fragaria × ananassa) caused by the ubiquitous necrotroph Botrytis cinerea, renders fruit unmarketable and causes economic losses in the postharvest supply chain. To explore the feasibility of selecting for increased resistance to gray mold, we undertook genetic and genomic prediction studies in strawberry populations segregating for fruit quality and shelf life traits hypothesized to pleiotropically affect susceptibility. As predicted, resistance to gray mold was heritable but quantitative and genetically complex. While every individual was susceptible, the speed of symptom progression and severity differed. Narrow-sense heritability ranged from 0.38 to 0.71 for lesion diameter (LD) and 0.39 to 0.44 for speed of emergence of external mycelium (EM). Even though significant additive genetic variation was observed for LD and EM, the phenotypic ranges were comparatively narrow and genome-wide analyses did not identify any large-effect loci. Genomic selection (GS) accuracy ranged from 0.28 to 0.59 for LD and 0.37 to 0.47 for EM. Additive genetic correlations between fruit quality and gray mold resistance traits were consistent with prevailing hypotheses: LD decreased as titratable acidity increased, whereas EM increased as soluble solid content decreased and firmness increased. We concluded that phenotypic and GS could be effective for reducing LD and increasing EM, especially in long shelf life populations, but that a significant fraction of the genetic variation for resistance to gray mold was caused by the pleiotropic effects of fruit quality traits that differ among market and shelf life classes.

Dynamic Microbiome Changes Reveal the Effect of 1-Methylcyclopropene Treatment on Reducing Post-harvest Fruit Decay in "Doyenne du Comice" Pear.

Pathogen-induced decay is one of the most common causes of fruit loss, resulting in substantial economic loss and posing a health risk to humans. As an ethylene action inhibitor, 1-methylcyclopropene (1-MCP) can significantly reduce fruit decay, but its effect on fruit pathogens remains unclear. Herein, the change in microbial community structure was analyzed using the high-throughput sequencing technology, and characteristics related to fruit quality were determined after 1-MCP (1.0 M l L–1) treatment in “Doyenne du Comiceis” pear fruit during storage at ambient temperature. Overall, 1-MCP was highly effective in reducing disease incidence and induced multiple changes of the fungal and bacterial microbiota. At day 15, the microbial diversity of fungi or bacteria was reduced significantly in the control fruit (non-treated with 1-MCP), which had the most severe decay incidence. For fungi, in addition to Alternaria being the most abundant in both 1-MCP treatment (59.89%) and control (40.18%), the abundances of Botryosphaeria (16.75%), Penicillium (8.81%), and Fusarium (6.47%) increased significantly with the extension of storage time. They became the primary pathogens to cause fruit decay in control, but they were markedly decreased in 1-MCP treatment, resulting in reduced disease incidence. For bacteria, the abundance of Gluconobacter (50.89%) increased dramatically at day 15 in the control fruit, showing that it also played a crucial role in fruit decay. In addition, Botryosphaeria, Fusarium fungi, and Massilia, Kineococcus bacteria were identified as biomarkers to distinguish 1-MCP treatment and control using Random Forest analysis. The redundancy analysis (RDA) result showed that the amount of Botryosphaeria, Penicillium, and Fusarium were positively correlated with disease incidence and respiration rate of pear fruits while negatively correlated with fruit firmness. This investigation is the first comprehensive analysis of the microbiome response to 1-MCP treatment in post-harvest pear fruit, and reveals the relationship between fruit decay and microbial composition in pear fruit.

Potential of Antifungal Proteins (AFPs) to Control Penicillium Postharvest Fruit Decay.

Penicillium phytopathogenic species provoke severe postharvest disease and economic losses. Penicillium expansum is the main pome fruit phytopathogen while Penicillium digitatum and Penicillium italicum cause citrus green and blue mold, respectively. Control strategies rely on the use of synthetic fungicides, but the appearance of resistant strains and safety concerns have led to the search for new antifungals. Here, the potential application of different antifungal proteins (AFPs) including the three Penicillium chrysogenum proteins (PAF, PAFB and PAFC), as well as the Neosartorya fischeri NFAP2 protein to control Penicillium decay, has been evaluated. PAFB was the most potent AFP against P. digitatum, P. italicum and P. expansum, PAFC and NFAP2 showed moderate antifungal activity, whereas PAF was the least active protein. In fruit protection assays, PAFB provoked a reduction of the incidence of infections caused by P. digitatum and P. italicum in oranges and by P. expansum in apples. A combination of AFPs did not result in an increase in the efficacy of disease control. In conclusion, this study expands the antifungal inhibition spectrum of the AFPs evaluated, and demonstrates that AFPs act in a species-specific manner. PAFB is a promising alternative compound to control Penicillium postharvest fruit decay.

Biofumigation activities of volatile compounds from two Trichoderma afroharzianum strains against Fusarium infections in fresh chilies.

Two Fusarium fungi, F. oxysporum and F. proliferatum, have been recognized as major pathogenic fungi that cause postharvest decay of chili fruits. Ozone and some toxic chemicals are used to control pathogenic infections, leading to longer storage lives of agricultural commodities. However, these chemicals may pose some risks to the applicators and the environment. Therefore, alternative, easy-to-use fumigants for effective control of Fusarium infections in harvested fresh chilies are needed. Two endophytic fungi, Trichoderma afroharzianum strain MFLUCC19-0090 and T. afroharzianum strain MFLUCC19-0091, were isolated from Schefflera leucantha leaves. Their volatile compounds were investigated for antifungal activities against F. oxysporum and F. proliferatum. In vitro results showed that the volatile compounds produced by each strain inhibited pathogen growth. Additionally, the Trichoderma-derived volatile compounds significantly reduced Fusarium-related disease severity and incidence percentages in the inoculated fresh chilies. Antifungal properties of the volatile compounds were found to be specific to the species of the tested pathogens (MFLUCC19-0090 greatly suppressed F. oxysporum and MFLUCC19-0091 greatly suppressed F. proliferatum). Seventy-three volatile compounds were detected from both strains. Among the major volatile compounds detected, phenyl ethyl alcohol was found to possess the strongest antifungal activity against both pathogens. These Trichoderma-derived volatile compounds may be used as alternative fumigants for controlling Fusarium rot in harvested fresh chilies. The successful use of volatile compounds as biofumigants can prevent significant market losses and, more importantly, may reduce the health hazards caused by Fusarium-associated mycotoxin exposures among consumers. © 2021 Society of Chemical Industry.

Genome-Wide Association Study of Brown Rot (Monilinia spp.) Tolerance in Peach.

Brown rot, caused by Monilinia spp., is one of the most important diseases on stone fruit worldwide. Severe yield loss can be caused by pre- and post-harvest fruit decay. Although some degree of tolerance has been reported in peach and almond, the genetic resistance in peach cultivars is still lacking. To date, only few genomic regions associated with brown rot response in fruit skin and flesh have been detected in peach. Previous studies suggested brown rot tolerance in peach being a polygenic quantitative trait. More information is needed to uncover the genetics behind brown rot tolerance in peach. To identify the genomic regions in peach associated with this trait, 26 cultivars and progeny from 9 crosses with ‘Bolinha’ sources of tolerance, were phenotyped across two seasons (2015 and 2016) for brown rot disease severity index in wounded and non-wounded fruits and genotyped using a newly developed 9+9K peach SNP array. Genome wide association study using single- and multi-locus methods by GAPIT version 3, mrMLM 4.0, GAPIT and G Model, revealed 14 reliable SNPs significantly associated with brown rot infection responses in peach skin (10) and flesh (4) across whole genome except for chromosome 3. Candidate gene analysis within the haplotype regions of the detected markers identified 25 predicted genes associated with pathogen infection response/resistance. Results presented here facilitate further understanding of genetics behind brown rot tolerance in peach and provide an important foundation for DNA-assisted breeding.

Discovery of natural fungicidal principles from the plant sources for effective management of chilli anthracnose

Anthracnose of chilli causes pre- and post-harvest fruit decay, resulting in significant yield losses. We surveyed major chilli growing regions in India and identified six Colletotrichum sp. viz., Colletotrichum truncatum, C. gloeosporioides, C. siamense, C. fructicola, C. karstii and C. cliviicola based on morphological characteristics and phylogenetic analysis of 115 pure cultures isolated from symptomatic fruits. Antifungal potential of aqueous, acetone, ethyl acetate and methanol extract of 52 plant parts comprising 28 families were evaluated against all identified Colletotrichum sp. Out of these, aqueous extracts (30%) of Syzygium aromaticum, Cinnamomum zeylanicum, Allium sativum and Phyllanthus emblica completely inhibited mycelial growth and conidial germination and solvent extracts (5 mg) showed a clear growth inhibition zone in vitro against Colletotrichum sp. Aqueous extract of S. aromaticum and ethyl acetate extract of C. zeylanicum was strongest as observed shrinking of cell components and maximum zone of inhibition (60 mm) of Colletotrichum sp., respectively.

How siderophore production can influence the biocontrol activity of Aureobasidium pullulans against Monilinia laxa on peaches

In the present study Aureobasidium pullulans strains L1 and L8 were shown both in vitro and in vivo to compete for iron with Monilinia laxa through the secretion of siderophores (1.2 and 1.4 mg ml−1, respectively) and to prevent postharvest fruit decay of peaches. The two strains reduced mycelial growth and conidial germination of M. laxa specially in presence of lower iron concentrations (5 and 10 µg l−1 FeCl3), confirming a better efficacy when nutrients are scarce. In in vivo assay, A. pullulans L1 and L8 strains inhibited pathogen virulence, reducing by 83.5% and 84.4% on average respectively the peach lesion diameter for each tested iron solutions (5, 10, 20 µg l−1 FeCl3,). The highest iron solution slowed down the antagonists’ action and conversely increase the pathogen aggressiveness. Results shows that A. pullulans L1 and L8 strains compete with M. laxa for iron, so revealing new biocontrol aspects. Both strains showed the capability to decrease the accumulation of iron competing with some fungal pathogens and reducing their virulence. These results provide new perspectives for the use of biocontrol agents in agriculture.

Inhibitory effect of gamma irradiation on Penicillium digitatum and its application in the preservation of Ponkan fruit

Penicillium digitatum is a fungal pathogen, mainly responsible for postharvest decay of citrus fruits. Herein, we investigated the effect of gamma irradiation on fungal growth and postharvest physiology of Ponkan mandarin (Citrus reticulata Blanco). Preliminary results revealed that high dose gamma irradiation (> 1 kGy) severely damaged the fruit. Thus, we evaluated the effect of lower doses of gamma radiation (0, 0.25, 0.50, 0.75, 1.0 kGy) on disrupting the growth of P. digitatum, as well as on the postharvest quality of the Ponkan fruit. We found that there was an inverse dose-dependence to gamma irradiation-mediated inhibition of P. digitatum growth. Next, we examined the membrane integrity in the fungi that were exposed to gamma radiation to understand the underlying mechanism of the observed growth inhibition. The gamma irradiation disrupted the fungal membrane, resulting in the leakage of intracellular contents, such as sugars and proteins out of the damaged cells. Moreover, the irradiation impaired the metabolic functioning of malate dehydrogenase (MDH) and succinate dehydrogenase (SDH) within the tricarboxylic acid cycle (TCA) cycle. The overall results showed that at room temperature, the preservative effects of 0.25 and 0.75 kGy radiation were not evident, whereas 1.0 kGy resulted in rapid aging of the Ponkan fruit; 0.5 kGy was the optimal radiation dose to slow down the rate of fruit decay whilst decreasing the nutrient and weight loss in storage. Additionally, 0.5 kGy irradiation reduced the content of malondialdehyde (MDA), resulting in the improved activity of superoxide dismutase (SOD), catalase (CAT), and peroxidase (POD). Thus, these findings suggest that the optimal dosage of gamma radiation had the potential to extend the room temperature storage life of Ponkan fruit.

Anti-fungal activity of phenolic sweet orange peel extract for controlling fungi responsible for post-harvest fruit decay

There is a growing interest in finding safe and natural anti-microbial compounds as a valid alternative to conventional chemical treatments for managing post-harvest fruit diseases. This study investigated the anti-fungal capacity of orange peel polyphenolic extract (OPE) against three relevant post-harvest fungal pathogens, Monilinia fructicola, Botrytis cinerea and Alternaria alternata. OPE extract at 1.5 g/L inhibited (100%) the mycelial growth and conidial germination of the three target fungi. At lower concentration, the effect varied, depending on the dose applied and target fungi. When the anti-fungal activity of the main phenolic compounds in sweet orange peel, namely, the flavonoids (naringin, hesperidin and neohesperidin) and phenolic acids (ferulic and p-coumaric), were evaluated, ferulic acid and p-coumaric acid displayed significantly higher inhibitory capacity in synthetic medium, while the activity of flavonoids was limited. Synergism between compounds was not detected, and the inhibitory activity of OPE may be attributed to an additive effect of phenolic acids. Interestingly, in peach-based medium, ferulic acid remained active against M. fructicola and A. alternata and was more efficient than p-coumaric to control B. cinerea. These results highlight peel orange waste as an excellent source of anti-fungal compounds, suggesting the possibility of using ferulic acid or ferulic acid-rich extracts, either alone or in combination with other post-harvest treatment, as a natural alternative to reduce post-harvest losses and, also, enhance the shelf-life of fruit.

Detection of quiescent fungi in harvested fruit using CMOS biosensor: A proof of concept study

Postharvest fruit decay is caused by fungal pathogens and leads to major losses. In this study, specific mRNA sequences that are upregulated in the fungus Colletotrichum gloeosporioides during its quiescent stage in fruits, were identified using a CMOS sensor. The identification process was based on sandwich approach, where strands complementary to the C. gloeosporioides mRNA sequences (quiescent stage-specific) were immobilized on the CMOS surface, and exposed to the target complementary reporter strands. In the presence of a target sequence, the reporter strand (linked to the enzyme horseradish peroxidase (HRP)) was left in the system and a measurable light signal was produced. The complementary strands specifically anneal to the mRNA in the sample. The sensitivity of the technology was assessed by mRNA sequences isolated from C. gloeosporioides, and identified as 10 nM RNA. The effect of the pathogenicity state on the sensor performance was also evaluated. The CMOS sensor could detect quiescent fungi, which are barely detectable by other means. The unique capability of the proposed system to detect and recognize the fungus during both pathogenic and quiescent stages, will allow the development of new sensors that can monitor the amount of undetectable quiescent fungi in harvested fruit, enabling improved food management.

PCR and Sequencing Base Detection of Gummosis Disease on Citrus aurantifolia Caused by Lasiodiplodia theobromae and Evaluation of Its Antagonisms

Diplodia gummosis disease caused by Lasiodiplodia theobromae is an economically important postharvest fruit decay that occurs on all types of citrus grown in Bangladesh. The present investigation was conducted to isolate and identify the pathogenic fungus responsible for postharvest diplodia gummosis disease (DGD) of citrus as well as the evaluation of its biological control through microbial antagonists. DGD causing pathogen was identified by physiological, morphological and molecular methods. The pathogenic fungus was isolated from the surface of postharvest lime fruits. The optimum growth of the fungi was observed in maltose, 2% NaCl, 15% sugar and pH 7 containing PDA medium at 35⁰C. PCR products of the internal transcribed spacer (ITS) region of the fungus showed approximately 650 bp size clear band in gel electrophoresis. The amplified region of the fungus showed 99.62% similarities with the sequences of L. theobromae. Artificially inoculation of the fungus in malta, musumbi, sweet orange, lime, and guava fruits showed similar size clear band and typical diplodia gummosis disease symptom. Methanol extracts of Datura metal displayed the highest inhibition (75.25%) against the isolated fungus. Non-pathogenic fungi Trichoderma viride showed the highest antagonistic efficiency followed by Neofusicoccum mangifera against the isolated fungus. The tested soil bacteria did not show significant antagonistic activity against the isolated fungus. Therefore, the DGD of citrus control system should be integrated into the overall citrus postharvest decay control system to reduce all citrus postharvest diseases and to protect fresh citrus fruit values.

Biological Control of Coniella granati Saccardo in Pomegranate

Coniella granati Saccardo (Synonym Pilidiella granati) is a fungal pathogen that causes fruit brown rot, cankers on shoots and crown rot of pomegranate trees. Although cultural and chemical control is recommended against C. granati; cultural control is not enough and limited number of advisable fungicides used in chemical control against this pathogen. Therefore, alternative strategies are needed for this pathogen control. In this context, it was aimed to investigate the effect of some bacterial biocontrol agents against C. granati under in vitro conditions. Dual culture of eleven bacterial biocontrol agents [1 Bacillus megaterium (TV 3D), 3 Bacillus substilis (TV 6F, TV 17C, CP1), 1 Bacillus cereus (TV 85D), 1 Paenibacillus polymxa (TV 12E), 2 Pseudomonas fluorescens (MF 3, AR 9), 1 Burkholderia cepacia (BA 7) 1 Pantoea agglomerans (MF 1) and 1 Bacillus thuringiensis (BAB 420)] were tested for antagonistic properties against C. granati. Percent inhibition rate values changed from 11.90% to 66.67% in dual culture. B. cereus (TV 85D, 66.67%) was the most effective strains against C. granati respectively by B. substilis (TV 17C, 64.29%; TV 6F, 60.71%) in in vitro. As a result, promising results were obtained from these isolates in in vitro conditions. These isolates should be tested in vivo conditions for controlling the post-harvest decay of pomegranate fruits caused by C. granati.

Potential modes of action of Pseudomonas fluorescens ZX during biocontrol of blue mold decay on postharvest citrus.

The application of chemical fungicides is currently the main method for the control of postharvest decay of fruits and vegetables. However, public concern has been growing towards the effect of fungicides on food safety, human health and environmental pollution. Thus, interest in microbial biocontrol agent development has grown, such agents being considered both safe and environmentally friendly. Pseudomonas fluorescens is widely distributed in nature, and one of the most valuable biocontrol and plant growth-promoting rhizobacteria. In this study, the efficacy and the potential associated modes of action of P. fluorescens ZX against Penicillium italicum on oranges (Citrus sinensis Osbeck) were investigated. The application of P. fluorescens ZX significantly reduced blue mold lesion size and incidence in comparison to the control, where P. fluorescens ZX was effective when applied preventatively but not curatively. In dual cultures, treatment with cell-free autoclaved cultures or culture filtrate had a limited capacity to suppress P. italicum, while P. italicum was inhibited by bacterial fluid and bacterial suspension with living cells in vitro. The P. fluorescens ZX isolate displayed protease, but not chitinase, glucanase or cellulose, activity, and produced siderophores and volatile organic compounds with antifungal abilities. Competition tests showed P. fluorescens ZX could use fructose, sucrose, aspartic acid, threonine, serine, glycine, valine, lysine and proline better than P. italicum. Furthermore, an effective biofilm that peaked after a 24-hour incubation at 30 °C was formed by the P. fluorescens ZX isolate. Light microscopy and scanning electron microscopy observations indicate the P. fluorescens ZX isolate could not undergo direct parasitism or hyperparasitism. Competition for nutrients and niches, biofilm formation, inhibition of spore germination and mycelial growth, and production of inhibitory metabolites may play important roles in P. fluorescens ZX antagonism of P. italicum. © 2019 Society of Chemical Industry.

Postharvest fungal fruit decay in sweet cherry graded in water with low chlorine content

Postharvest fungal fruit decay in sweet cherry graded in water with low chlorine content

Microbiome Response to Hot Water Treatment and Potential Synergy With Biological Control on Stored Apples.

Postharvest food decay is one major issue for today’s food loss along the supply chain. Hot water treatment (HWT), a sustainable method to reduce pathogen-induced postharvest fruit decay, has been proven to be effective on a variety of crops. However, the microbiome response to HWT is still unknown, and the role of postharvest microbiota for fruit quality is largely unexplored. To study both, we applied a combined approach of metabarcoding analysis and real time qPCR for microbiome tracking. Overall, HWT was highly effective in reducing rot symptoms on apples under commercial conditions, and induced only slight changes to the fungal microbiota, and insignificantly affected the bacterial community. Pathogen infection, however, significantly decreased the bacterial and fungal diversity, and especially rare taxa were almost eradicated in diseased apples. Here, about 90% of the total fungal community was composed by co-occurring storage pathogens Neofabraea alba and Penicillium expansum. Additionally, the prokaryote to eukaryote ratio, almost balanced in apples before storage, was shifted to 0.6% bacteria and 99.4% fungi in diseased apples, albeit the total bacterial abundance was stable across all samples. Healthy stored apples shared 18 bacterial and 4 fungal taxa that were not found in diseased apples; therefore, defining a health-related postharvest microbiome. In addition, applying a combined approach of HWT and a biological control consortium consisting of Pantoea vagans 14E4, Bacillus amyloliquefaciens 14C9 and Pseudomonas paralactis 6F3, were proven to be efficient in reducing both postharvest pathogens. Our results provide first insights into the microbiome response to HWT, and suggest a combined treatment with biological control agents.

Analysis of Critical Control Points of Post-Harvest Diseases in the Material Flow of Nam Dok Mai Mango Exported to Japan

‘Nam Dok Mai’ mango is a luxury commercial fruit in Thailand, but post-harvest diseases infecting the ripe fruit is a major problem affecting marketability. The objective of the present study was to map the supply chain of ‘Nam Dok Mai’ mangoes exported to Japan and analyze the critical points of post-harvest disease infection caused mainly by Colletotrichum gloeosporioides. Risk points of the post-harvest diseases were found by examining the material and information flows from processes ranging from field production to post-harvest handling, and these were obtained from mango growers and an exporter. The findings of interviews with mango growers and observations of the mangoes in field production were that the first point of risk was cultivar selection, while branch pruning and fruit bagging were further important processes causing post-harvest fruit decay. On the other hand, it was found that post-harvest handling was significant in decreasing anthracnose disease infection; this was seen at the step of dipping the fruit in 50 °C hot water for 3 min at the processing line.

Proline Increases Pigment Production to Improve Oxidative Stress Tolerance and Biocontrol Ability of Metschnikowia citriensis.

Utilizing antagonistic yeasts is a promising approach for managing postharvest decay of fruits. However, it is well established that various severe stresses encountered in the environment and production process cause the intracellular reactive oxygen species (ROS) accumulation in yeast cells, resulting in cell damage and loss of vitality. Here, proline has been shown to function as a cell protectant and inducer of biofilm formation able to increase the oxidative stress tolerance and the biocontrol ability of the antagonistic yeast Metschnikowia citriensis. Addition of proline to M. citriensis cells induced a significant rise in superoxide dismutase (SOD) and catalase (CAT) activity in the early and late stages of oxidative stress, respectively, and increased the maroon pigment production that directly reduced intracellular iron content and indirectly diminished intracellular ROS levels and thus inhibited ROS- and iron-induced apoptosis. Treating cells with iron chelator tropolone yielded similar results. Pigment production induced by proline also enhanced the capability of biofilm formation of M. citriensis. These results suggested an important role for pigment of M. citriensis in response to oxidative stress. The abilities of proline to scavenge intracellular ROS and inhibit apoptosis, increase pigment production, and promote biofilm formation contribute to the improvements in oxidative stress tolerance and biocontrol efficacy of M. citriensis.

Timing the application of Bacillus subtilis QST 713 in the integrated management of the postharvest decay of mango fruits

This work evaluated the application of a commercial formulation of B. subtilis QST 713 (Serenade®, Bayer AgroSciences) at different times in the development of mango fruits for the control of postharvest diseases. Initially, two experiments were conducted to define the best fruit development stage for substitute synthetic fungicides by biocontrol. The experiments were made in commercial orchards with cv. ‘Kent’ and ‘Palmer’ with five treatments: 1. Conventional – fungicides were applied from pre-bloom until the maximal growth of fruits and in the postharvest processing; 2. B. subtilis QST 713 substitute fungicides from the 50% flowering stage onwards and in postharvest treatment; 3. B. subtilis from the fruit-setting (peanut size) up to egg size and in postharvest; 4. B. subtilis from the fruit growth (from egg size until harvest) and in postharvest; 5. Preharvest – three weeks before harvest and in postharvest. Application of B. subtilis from the fruit setting and fruit growth stages onwards resulted in significantly lowest fruit rot incidence. A third experiment was conducted in an orchard with cv. Tommy Atkins and B. subtilis application started in three fruit development stages: 1. Conventional; 2. Fruit growth; 3. Preharvest. There was a significant reduction of rot incidence, severity, and lesion development rate through the shelf life period for the application starting fruit growth onward. Our results showed that B. subtilis QST 713 applied after the mid-stage of fruit development can efficiently complement the application of fungicides in the initial stages of mango fruit production. It is an important finding showing a safe substitution of conventional fungicides by a biofungicide formulation for the management of postharvest rot of mango.

Fungi Associated With Post-harvest Avocado Fruit Rot at Jimma Town, Southwestern Ethiopia

The poor post-harvest handling of avocado in and around Jimma was contribute its part for Post-harvest decay of avocado fruits and loss in quality of avocado. Besides, Post-harvest disease can limit the storage period for the fruit. The aim of this study was to identify Post-harvest pathogens affecting avocado fruits in Jimma town. A total of 35 avocado fruits categorized as apparently healthy (20), diseased (10) and decayed (5) avocado fruits were sampled from wholesalers, local market and farmers' field during 2017. A total of 30 fungal isolates were recovered and grouped into nine fungal species under eight genera. Botryotinia was the most frequently isolated genus (26.67%) followed by Colletotrichum (23.33%) and Aspergillus (10%). Thus, requests the need of management strategy that targets in reducing factors that facilitates the occurrence of fungal infection such options are avoidance of avocado fruit damaging practices by using locally available cushioning materials during loading to cars, avoiding loading of people and other materials together with avocado fruits on the same car, improving avocado storage houses to allow air circulation and avoiding damping of avocado fruits in the storage house.