Postharvest Rot Research Articles

Isolation and Identifi cation of Postharvest Fungal Pathogens of Some Selected Fruits in Yunnan, China

Fruits are one of the major economic commodities worldwide and postharvest rot diseases is one of the major problems that led to decreasing fruit production. Fungal contaminants reduce the quality of fresh fruits after harvest and it is one of the leading causes of economic loss in global fresh fruits. The purpose of this research was to isolate and identify pathogens causing postharvest rots on common fruits available in markets in Panlong District, Kunming, Yunnan Province, China. The fruits viz. apple (Malus domestica), dragon fruit (Hylocereus undatus), peach (Amygdalus persica) and pear (Pyrus sorotina) were selected to examine post-harvest rots since they are commonly available fruits in Yunnan markets. We isolated six fungal strains from the above-mentioned fruits. The pathogenicity tests and phylogenetic analyses were carried out for the fungi isolated from fruits. Our results showed that Fusarium spp. are common on apple, peach and dragon fruit. In the pathogenicity test, Monilinia yunnanensis inoculated on the pear had the strongest effect on the pear, and the disease spot expanded over half of the total area of the fruit. Our results are expected to provide a reference and basis for preventing postharvest diseases of common fruits in Yunnan.

The biostimulant effect of an extract from Durvillaea potatorum and Ascophyllum nodosum is associated with the priming of reactive oxygen species in strawberry in south-eastern Australia

AbstractStrawberry is an important horticultural crop in Victoria, Australia. Grey mould caused by Botrytis cinerea reduces marketable yield and post-harvest quality of strawberry fruit in the region. We conducted two field experiments in Victoria (Coldstream and Warburton) to evaluate the effectiveness of a commercial seaweed extract from Durvillaea potatorum and Ascophyllum nodosum (Seasol®) on the yield, revenue, and post-harvest rot of strawberry fruit. We applied the extract to strawberry crops (cv. Albion) monthly as a combined drench (10 L ha-1) and foliar spray (1:400), with water as a control. Application of the seaweed extract significantly increased strawberry fruit yields by 8-10% and revenue by AU$0.37-0.59 per plant. Furthermore, the extract significantly reduced the incidence and severity of post-harvest rots in strawberry fruit by 52-87%, respectively. The extract did not affect the firmness, soluble solids concentration (SSC), titratable acidity, or SSC:acid of strawberry fruit. In a separate laboratory experiment, we found that growing strawberry in the seaweed extract (1:400) increased the concentration of peroxidase by 50% and doubled H2O2 in roots soon after treatment. Increases in reactive oxygen species are an indicator of a suite of pathways associated with resistance and tolerance of biotic and abiotic stresses. Overall, the results demonstrate that the seaweed extract can act as a commercially-viable biostimulant for strawberry fruit production in south-eastern Australia.

Isolation, identification, and host range of Aspergillus welwitschiae causing postharvest rot on Chinese cabbage in China

A new kind of postharvest rot on Chinese cabbage (Brassica rapa L. ssp. pekinensis) caused by a fungus was observed in vegetable cellars in Harbin, China in 2019 and 2020, causing considerable economic losses. A water-soaked spot appeared at the base of the midrib of leaves, extended into the upper part of the midrib, and ultimately turned into rot. The diseased part was dark brown or black with a few black spores on the surface. Fungal isolates were obtained from the diseased plants and identified as Aspergillus welwitschiae through morphological observation and multigene sequencing analysis of the internal transcribed spacer, β-tubulin and calmodulin genetic regions. Pathogenicity tests were conducted, and the resulting symptoms on Chinese cabbage were similar to those seen in the vegetable cellar. The isolates were also associated with rot and leaf spot on seedlings and affected the seed germination of Chinese cabbage. A host range test showed that the isolates could infect some common vegetables, including carrot, kidney bean, broccoli, radish, Chinese flowering cabbage, root-mustard, cabbage, non-heading Chinese cabbage, pepper, lettuce, oilseed rape, tomato and cucumber. The isolation, identification, and host range of the pathogen can provide a basis for the study of the occurrence, prevention and management of the disease in the future.

Tannic acid exerts antifungal activity in vitro and in vivo against Alternaria alternata causing postharvest rot on apple fruit

Alternaria alternata is one of the main pathogens that causes black spot rot of apple fruit, mainly postharvest. Also, A. alternata can attack many other fruits and vegetables in most of the world's natural environments. In this study, the antifungal efficacy of tannic acid (TA) against A. alternata and its potential mechanisms were investigated. An in vitro bioassay suggested that 5.0 mg mL−1 TA significantly inhibited the mycelial growth and spore germination of A. alternata. The enzyme activities of hexokinase, phosphofructokinase and pyruvate kinase in glycolytic metabolism were decreased in A. alternata treated with TA. The accumulation of glucose content and the reduction of pyruvate content in A. alternata further confirmed that TA may block the glycolytic metabolism of this fungus, resulting in insufficient energy supply for cells. In addition, TA immersion treatment significantly reduced the development of lesion areas on apple fruits caused by A. alternata and delayed fruit softening during the storage period. The application of TA also increased the activity of chitinase, β-1,3-glucanase and phenylalanine ammonialyase and the contents of total phenolic compounds and flavonoids in apple fruit, indicating the activation of defense-related enzymes and phenylpropane metabolites. TA could potentially be used to prevent and control postharvest Alternaria rot by exerting antifungal activity on A. alternata and inducing resistance in apple fruit.

A polymer-based gel fumigator, having a combination of Monarda citriodora essential oil (MEO) and hexanal: A solution for the postharvest rot and phytotoxicity of apple during storage

Apples are susceptible to various fungal infections following harvest, resulting in significant losses. This study aimed to develop an essential oil based gel formulation to control the postharvest rot of apples caused by Aspergillus foetidus CBS121.28 and increase their shelf life during storage. In vitro, minimal fungistatic and fungicidal doses of MEO and constituents acting in the vapour-phase were established. MFC (Minimum Fungicidal Concentration) for MEO was 1153.85 µL L−1 air, hexanal 384.62 µL L−1 air, and carvacrol 96.15 µL L−1 air. The combinatorial treatment of MEO and constituents indicated synergy (FICI 0.375) between MEO (144.23 µL L−1 air) and hexanal (96.15 µL L−1 air). In contrast, the combination of MEO and carvacrol was antagonistic. In vivo treatment of MEO and hexanal combination on apple fruit by direct fumigation resulted in phytotoxicity. However, the phytotoxicity was remediated using the gel formulations incorporating various concentrations of MEO and hexanal combinations (Carrageenan guar gum gel and soft gel), which showed a synergistic effect (FICI 0.25 and 0.375, respectively). The gel formulations reduced the weight loss, suppressed the degradation of ascorbic acid, and prevented the change of pH and total soluble solids of the stored apples. The antioxidant activity and total phenolic content also increased in the stored apples. These findings suggest that using MEO and hexanal in a gel formulation is a more effective and organic way to protect apples from Aspergillus rot for an extended storage period.

Genomic Resources of Four Colletotrichum Species (C.fioriniae, C. chrysophilum, C. noveboracense, and C.nupharicola) Threatening Commercial Apple Production in the Eastern United States.

The genus Colletotrichum includes nine major clades with 252 species and 15 major phylogenetic lineages, also known as species complexes. Colletotrichum spp. are one of the top fungal plant pathogens causing anthracnose and pre- and postharvest fruit rots worldwide. Apple orchards are imperiled by devastating losses from apple bitter rot, ranging from 24 to 98%, which is a serious disease caused by several Colletotrichum species. Bitter rot is also a major postharvest rot disease, with C. fioriniae causing from 2 to 14% of unmarketable fruit in commercial apple storages. Dominant species causing apple bitter rot in the Mid-Atlantic United States are C. fioriniae from the Colletotrichum acutatum species complex and C. chrysophilum and C. noveboracense from the C. gloeosporioides species complex (CGSC). C. fioriniae is the dominant species causing apple bitter rot in the Northeastern and Mid-Atlantic states. C. chrysophilum was first identified on banana and cashew but has been recently found as the second most dominant species causing apple bitter rot in the Mid-Atlantic. As the third most dominant pathogen, C. noveboracense MB 836581 was identified as a novel species in the CGSC, causing apple bitter rot in the Mid-Atlantic. C. nupharicola is a sister group to C. fructicola and C. noveboracense, also causing bitter rot on apple. We deliver the resources of 10 new genomes, including two isolates of C. fioriniae, three isolates of C. chrysophilum, three isolates of C. noveboracense, and two isolates of C. nupharicola collected from apple fruit, yellow waterlily, and Juglans nigra. [Formula: see text] Copyright © 2023 The Author(s). This is an open access article distributed under the CC BY-NC-ND 4.0 International license.

First report of Botryosphaeria dothidea causing postharvest rot of quince fruits in Serbia

First report of Botryosphaeria dothidea causing postharvest rot of quince fruits in Serbia

The Blueberry Fruit Mycobiome Varies by Tissue Type and Fungicide Treatment

The microbial ecology of agricultural products may provide crucial insights into the management of postharvest fruit rots. To investigate postharvest microbial communities of highbush blueberry ( Vaccinium corymbosum), five fungicide spray programs were evaluated for their influence on the mycobiome of fruit skin and within the fruit pulp. The mycobiome was characterized by sequencing amplicons of the internal transcribed spacer 1 (ITS1) region with primers ITS1f and ITS4 with the Illumina MiSeq 300bp v3 system. Two of the five programs utilized commercial biological fungicides, two utilized azoxystrobin, and one utilized a series of treatments to simulate a realistic disease management program. Fungicide applications reduced diversity of the fruit skin mycobiome ( R2 = 0.409, P = 0.0001) and had a moderate impact on the pulp mycobiome ( R2 = 0.233, P = 0.0001). The mycobiome of the fruit pulp was also more variable than the skin mycobiome. In comparison with the untreated controls, each fungicide treatment program had a strongly significant effect on the β diversity of the blueberry fruit skin mycobiome ( R2 = 0.53 to 0.73, P = 0.0001). In the pulp, three of the five treatments had moderate but significant effects on β diversity in comparison with the control ( R2 = 0.10 to 0.18, P = 0.0005 to 0.017). Most samples indicated that fungi belonging to genera Epicoccum, Papiliotrema, and Sporobolomyces were widely prevalent and abundant across treatments and tissues. Fruit pathogen Botrytis cinerea was particularly abundant in the pulp of three of the fungicide treatments. Results from this study provide a baseline for future exploration of postharvest rot pathology and provide a community context on how fungicides may alter fungal communities in agricultural systems.

Genome-Wide Identification of Sweet Orange WRKY Transcription Factors and Analysis of Their Expression in Response to Infection by Penicillium digitatum.

WRKY transcription factors (TFs) play a vital role in plant stress signal transduction and regulate the expression of various stress resistance genes. Sweet orange (Citrus sinensis) accounts for a large proportion of the world's citrus industry, which has high economic value, while Penicillium digitatum is a prime pathogenic causing postharvest rot of oranges. There are few reports on how CsWRKY TFs play their regulatory roles after P. digitatum infects the fruit. In this study, we performed genome-wide identification, classification, phylogenetic and conserved domain analysis of CsWRKY TFs, visualized the structure and chromosomal localization of the encoded genes, explored the expression pattern of each CsWRKY gene under P. digitatum stress by transcriptome data, and made the functional prediction of the related genes. This study provided insight into the characteristics of 47 CsWRKY TFs, which were divided into three subfamilies and eight subgroups. TFs coding genes were unevenly distributed on nine chromosomes. The visualized results of the intron-exon structure and domain are closely related to phylogeny, and widely distributed cis-regulatory elements on each gene played a global regulatory role in gene expression. The expansion of the CSWRKY TFs family was probably facilitated by twenty-one pairs of duplicated genes, and the results of Ka/Ks calculations indicated that this gene family was primarily subjected to purifying selection during evolution. Our transcriptome data showed that 95.7% of WRKY genes were involved in the transcriptional regulation of sweet orange in response to P. digitatum infection. We obtained 15 differentially expressed genes and used the reported function of AtWRKY genes as references. They may be involved in defense against P. digitatum and other pathogens, closely related to the stress responses during plant growth and development. Two interesting genes, CsWRKY2 and CsWRKY14, were expressed more than 60 times and could be used as excellent candidate genes in sweet orange genetic improvement. This study offers a theoretical basis for the response of CSWRKY TFs to P. digitatum infection and provides a vital reference for molecular breeding.

First Report of Lasiodiplodia brasiliensis Causing Root Rot on Watermelon in Brazil.

Watermelon (Citrullus lanatus (Thumb.) Matsum. & Nakai) is an important crop in Brazil both for export and domestic consumption. In October 2019, watermelon plants showing decline and root rot symptoms were surveyed in 16 commercial fields in Baraúna's municipality (Rio Grande do Norte, Brazil). The disease prevalence was 12.5%, and the average incidence was 5%. Affected root segments were cut into small pieces and surface-disinfected with 70% ethyl alcohol and 1.5 % NaOCl for 1 and 2 min, respectively. Tissues were plated onto potato dextrose agar (PDA) and incubated at 25°C for 7 days. Fungal colonies developed from the infected tissues were dark or greyish, and pure cultures were obtained by hyphal tip isolation technique. Six fungal isolates with the same morphology were obtained. Two of them were selected for morphological and molecular characterization (CFC-1123 and CFC-1124). Isolates grew rapidly in PDA, covering the entire surface of the Petri dishes within 3 days. The aerial mycelium was initially white, turning dark greenish-gray after 4 to 5 days of incubation at 25°C in the dark. Isolates produced pycnidia and conidia in water-agar medium with sterilized pine needles after 30 days of incubation at 25°C under near-UV light. The conidia were initially hyaline and brown with central transverse septum and longitudinal streaks when mature. Conidia were ellipsoid to oval (22.83 ± 3.1 µm long and 11.58 ± 1.5 µm wide). Based on morphological features, the isolates were initially identified as Lasiodiplodia sp. (Phillips et al. 2013). To confirm the identification, genomic DNA was extracted and the internal transcribed spacer (ITS) region as well as fragments of the translation elongation factor 1-α (TEF) and β-tubulin 2 (TUB) genes were amplified using the primer pairs ITS1/ITS4 (White et al. 1990), EF1-728F/EF1-986R (Carbone and Kohn 1999) and Bt2a/Bt2b (Glass and Donaldson 1995), respectively. The sequences were deposited in GenBank under accession numbers OL841380, OL865376 and OL890691 for CFC-1123, and OL841381, OL865377 and OL890692 for CFC-1124. Maximum likelihood phylogenetic analysis of the concatenated sequences of ITS, TEF and TUB gene regions of some reference sequences and ex-types of Lasiodiplodia spp. was performed. Phylogenetic analysis revealed that the isolates grouped in the L. brasiliensis clade (Netto et al. 2014) with 80/79% of bootstrap. The isolates were deposited in the Culture Collection of Phytopathogenic Fungi from Cariri (CFC) at the Universidade Federal do Cariri (Crato, Brazil). Pathogenicity of the two isolates was determined using colonized wheat grains as inoculum source. One watermelon seed (cv. Crimson Sweet) was placed in a sterile plastic pot (500-mL) filled with 6 cm layer of a substrate composed of soil and Tropstrato® (5:1 w/w). Three wheat grains (50 mg) colonized with each isolate were placed 10 mm above the seed and covered with the substrate. Control pots were inoculated only with sterile wheat grains. There were five replicates for each isolate. The pots with seedlings were maintained in a greenhouse at 28 ± 2°C under natural light conditions. The inoculated seedlings showed poor growth, withering and drying leaves 45 days after inoculation (DAI), and subsequently root rot symptoms and death at 60 DAI. Control seedlings remained asymptomatic. The pathogen was re-isolated from all inoculated seedlings and identified by conidia morphology to fulfill Koch's postulates. Lasiodiplodia brasiliensis has been reported to cause postharvest rot and gummosis of watermelon (Farr and Rossman 2022). However, to our knowledge, this is the first report of watermelon decline caused by this fungus in Brazil and worldwide. This finding must be considered for developing efficient control strategies for the disease.

Antifungal activity of diacetyl, a volatile organic compound, on Trichoderma lixii F2 isolated from postharvest Lanzhou lily bulbs

The most severe fungal disease is postharvest gray mold, which might cause massive losses in Lanzhou lily bulbs. Some microorganism-produced volatile organic compounds (VOCs) have been proven to have antifungal action and can be employed as fruit and vegetable preservation. Our most recent research discovered that diacetyl (2, 3-butanedione) produced by Bacillus subtilis CL2 could significantly prevent some pathogens. The goal of this investigation was to see if diacetyl had antifungal properties against Trichoderma lixii F2, one of the most common postharvest rot pathogens of Lanzhou lily bulbs. The results indicated that diacetyl (1.587 μL/mL) fumigation treatment significantly inhibited the hyphal growth, modified hyphal morphology, and disrupted the cell membrane integrity. In vivo tests the antifungal mechanisms of diacetyl on T. lixii F2 were performed in Lanzhou lily bulbs. The results indicated that the content of total phenols and flavonoids increased, while malondialdehyde decreased under different treatment by diacetyl. Meanwhile, the activities of peroxidase, polyphenol oxidase, catalase, and superoxide dismutase and phenylalanine ammonia-lyase in Lanzhou lily bulbs were investigated. It was showed that diacetyl could eliminate excessive reactive oxygen species, reduce the damage of plant cells, and improve the resistance of Lanzhou lily bulbs against T. lixii F2. This research reveals that diacetyl could activate antioxidant enzymes and disease-resistant enzymes in Lanzhou lily bulbs to prevent pathogenic fungus from invading and inducing resistance, laying the groundwork for future uses in preserving Lanzhou lily bulbs.

Morphological Diversity of Fungal Strains Responsible for Dessert Banana Rot, Musa Sapientum (Musaceae) Produced in the South Comoe Region on Ivory Coast

Aims: The banana dessert grown in different regions of the world, encounters important difficulties that cause it to lose its marketability especially because of the diseases related to conservation. The objective here is to identify the strains responsible for fungal diseases of bananas when it is stored.
 Study Design: This study was undertaken in order to ensure the competitiveness of the dessert banana from Ivory Coast on the international market which is threatened by the recurrent problem of post-harvest rot.
 Place and Duration of Study: Agrovalorisation Laboratory, Agroforestry Training and Research Unit, Université Jean Lorougnon GUEDE Daloa Côte d'Ivoire, between February 2021 and March 2022.
 Methodology: The study involved 120 bananas divided into two batches of 10 hands each, one with signs of necrosis and the other with no signs. Banana fragments (crown, epicarp and explant) were deposited on the growing media at several distinct points and slightly embedded in the agar. The resulting colonies were transplanted successively until a pure strain was obtained from a single mushroom colony per petri dish.
 Results: A total of 11 different genera were identified from 105 isolates. 57 are from necrotic bananas and 36 from bananas with no signs of necrosis. Fungal strains isolated there are: Trichoderma sp. (15%), Fusarium sp. (1%), Scytalidium sp. (39%), Mucor sp. (1%), Scopulariopsis sp. (1%), Alternaria sp. (4%), Aureobasidium sp. (1%), Aspergillus of the Glaucus group (10%), Cladosporium sp. (2%), Pseudallescheria sp. (6%) and Chrysosporium sp. (20%). No strains of the genus Colletotrichum musea responsible for anthracnose that can develop on both green and ripe fruit have been isolated. However, morphological characterization has not among to identify several other species (12) especially those not sporulating.
 Conclusion: This diversity of isolated strains in this work is identical to that most frequently isolated and cited in the literature.

Post-harvest assessment of infectious fruit rot on selected fruits in Lafia, Nasarawa State Nigeria

The post-harvest health and microbial safety of plant products and foods continue to be a global concern to farmers, consumers, regulatory agencies and food industries. A study was carried out to evaluate the pathogenicity of fungi associated with post-harvest rot of oranges, watermelons and bananas in Lafia, Nasarawa State, Nigeria. Healthy fruits inoculated with fungal spores obtained from rotted fruit tissues were incubated at ambient temperature conditions and observed daily for the appearance and development of tissue rot. Oranges and Watermelons had the highest number of fungal isolates (3) compared to banana (2). Fungi belonging to the genus Curvularia were the most isolated (37.50%), followed by both Aspergillus and Colletotrichum (25.00% respectively) and lastly Alternaria (12.50%). The highest tissue rot diameter of sweet orange (2.40 cm) was induced by Alternaria sp. followed by Curvularia geniculate (1.40 cm) and lastly Colletotrichum sp. (1.28 cm). The highest rot of banana fruit tissues was produced by A. niger (3.90 cm), followed by Curvularia geniculate (3.40 cm). Aspergillus sp. produced the highest tissue rot diameter on watermelon fruits (1.93 cm), followed by Colletotrichum sp. (1.30 cm) and lastly Curvularia geniculate (1.20 cm). Differences in the susceptibilities of different fruits to rot by fungal pathogens were significant (p ≤ 0.05). There is need for improved handling of fruits after harvest to prevent losses due to bacterial and fungal rots in the study area.

Effects of Certain Fungicide Alternatives on Garlic Yield, Storage Ability and Postharvest Rot Infection

Effects of Certain Fungicide Alternatives on Garlic Yield, Storage Ability and Postharvest Rot Infection

Determination of the antifungal effects of Isothiocyanate compounds against some fungal disease agents that cause postharvest rot in pepper fruits

Depolanmış ürünlerde sorun olan fungal hastalık etmenleri, hasat sonrası ürünlerde kaliteyi sınırlandıran önemli faktörlerden biridir. Hasat sonrası kurutulmalık biberler mikotoksin üreten fungal patojenler tarafından çok sık enfekte olmaktadırlar. Aspergillus niger, Alternaria alternata ve Fusarium incarnatum, birçok bitkide hasat öncesi ve sonrası dönemlerde hastalıklara neden olan potansiyel mikotoksin üretebilen önemli fungal etmenlerdir. Brassica spp. tarafından üretilen ve geniş antimikrobiyal etkiye sahip olan isothiocyanate (ITC)’lar, glukozinolatların biyolojik olarak aktif bozulma ürünleri ile bağlantılı allelokimyasal bileşiklerdir. Bu çalışmada, farklı kimyasal yapıdaki isothiocyanate bileşiklerden methyl isothiocyanate (MITC), 2-propenyl (Allyl) isothiocyanate (AITC), benzyl isothiocyanate (BITC) ve ethyl isothiocyanate (EITC)’ın Aspergillus niger, Alternaria alternata ve Fusarium incarnatum izolatlarına karşı in vitro antifungal etkileri araştırılmıştır. Test edilen Fusarium incarnatum, Aspergillus niger ve Alternaria alternata’nın misel gelişimini tamamen engelleyen konsantrasyonları (MIC) baz alındığında en yüksek antifungal etkinlik MITC tarafından sırasıyla 0.06, 0.09 ve 0.09 μl petri-1 konsantrasyonlarında gösterilmiştir. En düşük antifungal aktivite ise A. niger ile F. incarnatum’a karşı EITC (0.15 ve 0.21 μl petri-1), A. alternata’ya karşı ise AITC ve BITC (0.21 μl petri-1) tarafından gösterilmiştir. Farklı yapıdaki ITC’ların MIC değerlerinde genelde fungisidal etkiye sahip olduğu belirlenmiştir. Elde edilen sonuçlar, oldukça düşük konsantrasyonlarda antifungal etkinlik gösteren isothiocyanate’ların, depolanmış tarımsal ürünlerde bozulmalara neden fungal etmenlere karşı fumigant olarak olarak uygulanabilir potansiyele sahip olduğunu göstermiştir.

The antifungal activity and mechanism of silver nanoparticles against four pathogens causing kiwifruit post-harvest rot.

Post-harvest rot causes enormous economic loss to the global kiwifruit industry. Currently, there are no effective fungicides to combat the disease. It is unclear whether silver nanoparticles (AgNPs) are effective in controlling post-harvest rot and, if so, what the underlying antifungal mechanism is. Our results indicated that 75 ppm AgNPs effectively inhibited the mycelial growth and spore germination of four kiwifruit rot pathogens: Alternaria alternata, Pestalotiopsis microspora, Diaporthe actinidiae, and Botryosphaeria dothidea. Additionally, AgNPs increased the permeability of mycelium’s cell membrane, indicating the leakage of intracellular substance. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) observations revealed that AgNPs induced pathogen hypha shrinkage and distortion, as well as vacuolation in hypha cells, implying that AgNPs caused cellular and organelle structural degradation. The transcriptome sequencing of mycelium treated with AgNPs (24 h / 48 h) was performed on the Illumina Hiseq 4000 sequencing (RNA-Seq) platform. For the time points of 24 h and 48 h, AgNPs treatment resulted in 1,178 and 1,461 differentially expressed genes (DEGs) of A. alternata, 517 and 91 DEGs of P. microspora, 1,287 and 65 DEGs of D. actinidiae, 239 and 55 DEGs of B. dothidea, respectively. The DEGs were found to be involved in “catalytic activity,” “small molecule binding,” “metal ion binding,” “transporter activity,” “cellular component organization,” “protein metabolic process,” “carbohydrate metabolic process,” and “establishment of localization.” Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis also revealed that “carbohydrate metabolism,” “amino acid metabolism,” “energy metabolism,” and “xenobiotics biodegradation and metabolism” of “metabolism processes” were the most highly enriched pathways for these DEGs in four pathogens, with “cellular processes” being particularly enriched for B. dothidea. Furthermore, quantitative polymerase chain reactions (qPCRs) were used to validate the RNA-seq results. It was also confirmed that AgNPs could significantly reduce the symptoms of kiwifruit rot without leaving any Ag+ residue on the peel and flesh of kiwifruit. Our findings contributed to a better understanding of the antifungal effect and molecular mechanisms of AgNPs against pathogens causing kiwifruit post-harvest rot, as well as a new perspective on the application of this novel antifungal alternative to fruit disease control.

Volatiles of Zanthoxylum limoncello as Antifungal Agents against the Postharvest Rot of Manzano Pepper Triggered by Fusarium temperatum

The manzano pepper (Capsicum pubescens) is an exportation product that generates substantial earnings for local producers in Mexico. Herein we report on the most relevant metabolic changes that occur during the postharvest rot of manzano peppers caused by Fusarium temperatum. Simultaneously, we describe the effect of the Zanthoxylum limoncello leaf essential oil (ZlEO) and its major volatiles on the control of this devastating disease. According to our results, ZlEO, 2-undecanone (34%), 2-undecenal (32%), and 2-dodecenal (8%) exerted in vitro fungicide activity on F. temperatum (MIC, 104.6–218.3 mg L−1) and a strong in situ fungistatic effect in manzano peppers previously infected with F. temperatum. A differential fungistatic activity was observed for the natural agents assayed. However, the best results were confirmed with 2-dodecenal, which improved the shelf life of infected peppers up to 16 d post-inoculation. The protective effect of ZlEO and its major volatiles resulted in the conservation of fruit firmness, pH, protein, fat, fiber, ascorbic acid, and nutraceuticals of manzano peppers (carotenoids and capsaicinoids). Our findings endorse the potential use of ZlEO and its major volatiles as natural antifungals to prevent the soft rot triggered by F. temperatum.

From Glaciers to Refrigerators: the Population Genomics and Biocontrol Potential of the Black Yeast Aureobasidium subglaciale.

ABSTRACTApples are affected by numerous fungi known as storage rots, which cause significant losses before and after harvest. Concerns about increasing antimicrobial resistance, bans on various fungicides, and changing consumer preferences are motivating the search for safer means to prevent fruit rot. The use of antagonistic microbes has been shown to be an efficient and environmentally friendly alternative to conventional phytopharmaceuticals. Here, we investigate the potential of Aureobasidium subglaciale for postharvest rot control. We tested the antagonistic activity of 9 strains of A. subglaciale and 7 closely related strains against relevant phytopathogenic fungi under conditions simulating low-temperature storage: Botrytis cinerea, Penicillium expansum, and Colletotrichum acutatum. We also investigated a selection of phenotypic traits of all strains and sequenced their whole genomes. The tested strains significantly reduced postharvest rot of apples at low temperatures caused by B. cinerea, C. acutatum (over 60%), and P. expansum (about 40%). Several phenotypic traits were observed that may contribute to this biocontrol capacity: growth at low temperatures, tolerance to high temperatures and elevated solute concentrations, and strong production of several extracellular enzymes and siderophores. Population genomics revealed that 7 of the 15 strains originally identified as A. subglaciale most likely belong to other, possibly undescribed species of the same genus. In addition, the population structure and linkage disequilibrium of the species suggest that A. subglaciale is strictly clonal and therefore particularly well suited for use in biocontrol. Overall, these data suggest substantial biological control potential for A. subglaciale, which represents another promising biological agent for disease control in fresh fruit.IMPORTANCE After harvest, fruits are often stored at low temperatures to prolong their life. However, despite the low temperatures, much of the fruit is lost to rot caused by a variety of fungi, resulting in major economic losses and food safety risks. An increasingly important environmentally friendly alternative to conventional methods of mitigating the effects of plant diseases is the use of microorganisms that act similarly to probiotics—occupying the available space, producing antimicrobial compounds, and consuming the nutrients needed by the rot-causing species. To find a new microorganism for biological control that is particularly suitable for cold storage of fruit, we tested different isolates of the cold-loving yeast Aureobasidium subglaciale and studied their phenotypic characteristics and genomes. We demonstrated that A. subglaciale can significantly reduce rotting of apples caused by three rot-causing molds at low temperatures and thus has great potential for preventing fruit rot during cold storage.

Melatonin Enhances the Postharvest Disease Resistance of Blueberries Fruit by Modulating the Jasmonic Acid Signaling Pathway and Phenylpropanoid Metabolites.

In this study, to investigate the physiological and molecular mechanisms of melatonin inhibiting the postharvest rot of blueberry fruits, blueberry fruits were dipped in 0.3 mmol L−1 melatonin solution for 3 min and stored at 0°C for 80 days. The results indicated that melatonin did not significantly (p > 0.05) inhibit the mycelial growth or spore germination of Alternaria alternata, Botrytis cinerea, and Colletotrichum gloeosporioides. In addition, an in vivo study revealed that melatonin treatment increased the enzymatic activities of phenylalanine ammonia lyase (PAL), cinnamate 4-hydroxylase (C4H), 4-coumarate-CoA ligase (4CL), cinnamyl alcohol dehydrogenase (CAD), polyphenol oxidase (PPO), and peroxidase (POD) in fruits. Furthermore, genes related to jasmonic acid synthesis were upregulated (VaLOX, VaAOS, and VaAOC), as were those related to pathogenesis-related proteins (VaGLU and VaCHT) and phenylpropane metabolism (VaPAL, VaC4H, Va4CL, VaCAD, VaPPO, and VaPOD), which promoted the accumulation of total phenols, flavonoids, anthocyanins, and lignin in the fruits. These results suggest that melatonin enhances the postharvest disease resistance of blueberry fruits by mediating the jasmonic acid signaling pathway and the phenylpropane pathway.

First Report of Eucalyptus Wilt Caused by Chalaropsis thielavioides in China.

Eucalyptus species are widely planted in the tropics and subtropics, and eucalyptus is among the most important cash crop in Southern China. One of the most important diseases on eucalyptus is Ceratocystis wilt, caused by the fungus Ceratocystis fimbriata Ellis & Halst., and the genus name Chalaropsis has been proposed for anamorphs of Ceratocystis species (de Beer et al. 2014). During April 2018, severely infected Eucalyptus robusta trees were observed in Kunming, Yunnan Province, China. Symptomatic trees initially exhibited yellowing and wilting of foliage on individual branches, then spread to the whole canopy, sometimes followed by death of the whole tree. Reddish-brown to dark-brown discoloration in the woody xylem of affected trees, sometimes a grayish white layer of fungal growth may be seen. The disease was observed on 16% of trees surveyed. The base of trunks with typical symptoms were collected, then the discolored xylem tissues were surface disinfected with 75% ethanol for 30 s and 0.1% mercuric chloride (HgCl2) solution for 2 min, rinsed three times with sterile distilled water, plated onto potato dextrose agar (PDA) medium, and incubated at 25°C. After 6 days, a fungus was consistently observed growing from the tissue. Three isolates were obtained. In culture, colonies reaching 54mm diam within 15 days, mycelium initially white, then becoming celadon. Endoconidia unicellular, smooth, cylindrical, straight, biguttulate, 11.21 - 32.26 × 4.12 - 5.25 μm. Phialides produced on short, septate, aerial hyphae, lageniform and chain of phialoconidia (3.62 - 5.89 × 31.39 - 65.76 μm) were also observed. Chlamydospores (11.45 - 14.26 × 10.06 - 12.22 μm) were single, dark, thick-walled. Morphological characteristics of the fungus were consistent with the description of Chalaropsis thielavioides (Paulin-Mahady et al. 2002). The two of three isolates were used for molecular identification and genomic DNA was extracted from isolates (EKY2-2-1, EKY2-2-2) using the chelex-100 method (Xu et al. 2020). The ITS region of rDNA was sequenced using the procedures of Thorpe et al. (2005). Analysis of ITS sequence data (GenBank accessions MW242701, MW242702) showed that the isolates were 99% - 100% homologous to isolates of C. thielavioides from Hevea rubber, Monstera deliciosa L. and ants in China and Rosa sp. in Australia (GenBank accessions KT963172, KJ511482, KT963173 and KX954598) by BLAST analysis. Neighbor-joining (NJ) phylogenetic analysis were performed using MEGA 6.06 based on ITS sequences (Fig 1), the evolutionary distances were computed using the Maximum Composite Likelihood method. Analyses showed that both isolates (EKY2-2-1, EKY2-2-2) located on the same clade with all C. thielavioides, and clustered with the C. thielavioides strains with high bootstrap support (97% - 100%). Therefore, the fungus was identified as C. thielavioides based on morphology and molecular evidences. Pathogenicity of C. thielavioides was tested by inoculation of six one-year-old pot grown Eucalyptus citriodora seedlings. The sterilized soil of six seedlings was inoculated by drenching with 20 ml spore suspension (2.0 × 106 spores / ml). Control plants were inoculated with 20 ml of sterile distilled water. The seedlings were kept in a controlled greenhouse at 25°C and watered weekly. After one month incubation, all the isolates produced wilt symptoms, whereas control trees showed no symptoms. The original fungus was successfully re-isolated from inoculated trees and identified as C. thielavioides according to the methods described above, and no fungal growth was observed in the controls, thus satisfying Koch's postulates. Although wilt and canker caused by Ceratocystis fimbriata on eucalyptus have been previously reported in Brazil, Uruguay, Uganda, China and Pakistan (Ferreira et al. 1999; Li et al. 2014; Alam et al. 2017), eucalyptus wilt caused by C. thielavioides has not been reported anywhere. Also, wilt of rubber tree and postharvest rot on carrot caused by C. thielavioides have been reported (Li et al. 2021; Xu et al. 2020). To our knowledge, this is the first report of eucalyptus wilt caused by C. thielavioides in China.