Vishniacozyma victoriae: An endophytic antagonist yeast of kiwifruit with biocontrol effect to Botrytis cinerea

Eco-friendly biocontrol strategies for management of postharvest fungal decays in kiwifruit: A review

Kiwifruit is known for its rich content of nutrients and significant economic value. Global cultivation of kiwifruit has been increasing along with the amount of land being dedicated to its production. Regrettably, postharvest fungal decays, such as those caused by Botrytis cinerea, Penicillium expansum, Alternaria alternata, Botryosphaeria dothidea, Nigrospora oryzae, and others, pose a significant challenge to the kiwifruit industry, and are responsible for substantial losses during storage, transportation, and local marketing. Biological control of postharvest diseases is seen as a safe and sustainable strategy and as a result has received considerable interest for its potential in disease management. The present review provides an overview of the research conducted on the major postharvest diseases of kiwifruit and the use of biocontrol agents to manage these diseases. It also reviews the status of microbial formulations and the impact of environmental factors on biocontrol efficacy. The need for further research on the utilization of microbial consortia to manage postharvest diseases of kiwifruit is discussed as a major new approach to biological control.

Impact of Phage Therapy on Pseudomonas syringae pv. syringae and Plant Microbiome Dynamics Through Coevolution and Field Experiments

Bacteriophages (phages) are viruses that infect and lyse bacteria and have the potential for controlling bacterial diseases. Isolation of phages targeting the cherry pathogen Pseudomonas syringae pv. syringae (Pss) led to five distinct phage genotypes. Building on previous in vitro coevolution experiments, the coevolution of the five phages (individually and as a cocktail) with Pss on cherry leaves was conducted in glasshouse and field experiments. Phages effectively reduced Pss numbers on detached leaves, with no evidence of phage resistance emerging in the bacterial population. Field application of phages in a cherry orchard in Southeast England evaluated phage survival, viability and impact on bacterial populations and the microbial community. The bacterial population and phages persisted in the leaf and shoot environment as long as the bacterial host was present. In contrast to in vitro studies, the plant environment constrained the emergence of phage resistant Pss populations. Application of phage cocktail in the orchard did not affect the cherry leaf microbiome. These observations provide essential knowledge for using phage treatments to control bacterial diseases while minimising the impact on the plant microbiome, highlighting phages' potential to safely control bacterial diseases in trees.

Isolation of an endophytic yeast for improving the antibacterial activity of water chestnut Jiaosu: Focus on variation of microbial communities

Recent years have seen an increase in the development of functional Jiaosu products, including eco-friendly Jiaosu and antimicrobial healthcare fermentation products. As a result, research on the antibacterial activity of Jiaosu has attracted attention. In the present study, the endophytic yeast WCF016, which exhibits antibacterial activity against Escherichia coli and Staphylococcus aureus, was isolated from the peel of water chestnut and identified as Candida sake via morphological and phylogenetic analyses based on 26S rDNA D1/D2 region sequencing. Water chestnut Jiaosu with or without WCF016 inoculation exhibited similar flavor and physicochemical properties. However, inoculation significantly enhanced the antibacterial activity of water chestnut Jiaosu, especially in group D (inoculate of both fruit and vegetable enzyme starter and WCF016), which showed the largest diameter in its inhibition zone for both E. coli and S. aureus, reaching 25 ± 0 mm and 24 ± 1.0 mm. Moreover, inoculation with WCF016 influenced the abundance of the microbial community, especially Lactiplantibacillus and Zygoascus, which reached 51.76 % and 24.46 %, respectively, in group B (inoculated WCF016), thereby improving the antibacterial activity and flavor quality of the water chestnut Jiaosu. Notably, final pH, total sugar, and all organic acids effectively promoted fungal diversity and exhibited a positive correlation with most of the fungal genera. These results indicate that conditions conducive to the formation of organic acid-producing microbes and the synthesis of organic acids promote the antibacterial activity of Jiaosu.

Combination of atmospheric and room temperature plasma and ribosome engineering techniques to enhance the antifungal activity of Bacillus megaterium L2 against Sclerotium rolfsii

BACKGROUND

Sclerotium rolfsii is an extremely destructive phytopathogenic fungus that causes significant economic losses. Biocontrol strategies utilizing antagonistic microorganisms present a promising alternative for controlling plant pathogens. Bacillus megaterium L2 has been identified as a potential microbial biocontrol agent in our previous study; however, its efficacy in controlling pathogens has yet to meet current demands. This study aims to enhance the antifungal activity of strain L2 against S. rolfsii R-67 through a two-round mutagenesis strategy and to preliminarily investigate the mutagenesis mechanism of the high antifungal activity mutant.

RESULTS

We obtained mutant Dr-77 with the strongest antifungal activity against R-67, and its cell-free supernatant significantly reduced the infection potential of R-67 to Amorphophallus konjac corms, which may be attributed to the antimicrobial compound phenylacetic acid (PAA), and PAA content in Dr-77 (5.78 mg/mL) was 28.90 times higher than original strain L2. This compound exhibited strong antifungal ability against R-67, with a half maximal effective concentration (EC50) value of 0.475 mg/mL, significantly inhibiting mycelial growth and destroying the ultrastructure of R-67 at EC50 value. Notably, PAA also exhibited broad-spectrum antifungal activity against six phytopathogens at EC50 value. Moreover, genome analysis revealed nine different gene mutations, including those involved in PAA biosynthesis, and the activities of prephenate dehydratase (PheA) and phenylacetaldehyde dehydrogenase (ALDH) in PAA biosynthesis pathway were significantly increased.

CONCLUSION

These results suggest that the elevated PAA content is a primary factor contributing to the enhanced antifungal activity of Dr-77, and that this mutagenesis strategy offers valuable guidance for the breeding of functional microbial resources. © 2024 Society of Chemical Industry.

Biocontrol mechanisms of antagonistic yeasts on postharvest fruits and vegetables and the approaches to enhance the biocontrol potential of antagonistic yeasts

During storage and transportation, fruits and vegetables are susceptible to various pathogens, leading to quality degradation and significant economic losses. Currently, chemical pesticides are primarily used for control; however, their overuse poses serious threats to human health and causes environmental pollution. Biocontrol, known for its environmentally friendly characteristics, has been extensively studied. Among biocontrol agents, yeasts are widely distributed and possesses strong antagonistic abilities, making them crucial agents against numerous pathogenic fungi. Despite their considerable promise, the full potential of antagonistic yeasts for broader application remains untapped. Therefore, this paper reviews the mechanisms of antagonistic yeasts as biocontrol agents for postharvest diseases, including space and nutrients competition, competition for scarce iron resources, parasitism, production of soluble and volatile antifungal compounds, and induction of host systemic resistance. The paper also introduces research on the combined application of antagonistic yeasts with physical, chemical, and other microbial methods. Ultimately, this review provides a potential pathway to enhance the biocontrol effectiveness of antagonistic yeasts and expand their application prospects.

Five new epiphytic species of Vishniacozyma (Bulleribasidiaceae, Tremellales) from China

The genus Vishniacozyma, globally distributed, encompasses numerous epiphytic and endophytic species. In this study, five new species are proposed to accommodate eleven yeast strains isolated from leaves of different plants: V.diospyri sp. nov. (holotype CICC 33574T), V.guiyangensis sp. nov. (holotype CICC 33569T), V.pingtangensis sp. nov. (holotype CICC 33596T), V.eriobotryae sp. nov. (holotype GDMCC 2.312T), and V.tianchiensis sp. nov. (holotype CICC 33617T) using phenotypic and phylogenetic characters. Phylogenetic analysis was based on the internal transcribed spacer (ITS) region and the D1/D2 domain of the large subunit (LSU) rRNA gene. Illustrations and descriptions of these five taxa are provided, along with comparative analyses with closely related species within the genus. This research highlights the considerable diversity of Vishniacozyma species in China and contributes valuable data for future investigations in fungal systematics and evolution.

Spinach seed microbiome characteristics linked to suppressiveness against Globisporangium ultimum damping-off

Recently we demonstrated that the seed microbiome of certain spinach (Spinacia oleracea) seed lots can confer disease suppression against Globisporangium ultimum damping-off (previously known as Pythium ultimum). We hypothesized that differences in the microbial community composition of spinach seed lots correlate with the levels of damping-off suppressiveness of each seed lot. Here, we show that a large proportion of variance in seed-associated bacterial (16S) and fungal (Internal Transcribed Spacer 1) amplicon sequences was explained by seed lot identity, while 9.8% of bacterial and 7.1% of fungal community variance correlated with disease suppression. More specifically, a higher relative abundance of basidiomycetous dimorphic yeasts such as Vishniacozyma, Filobasidium, and Papiliotrema and of the bacterial genus Massilia was a key feature of suppressive seed microbiomes. We suggest that the abundance of these genera is indicative of seed lot suppressive potential. Seed processing and treatment can become more targeted with indicator taxa being used to evaluate the presence of beneficial seed-associated microbial functions. This process, in turn, could contribute to the sustainable management of seedling diseases. Finally, this study highlights the ubiquity of yeasts in spinach seed microbiota and their potential beneficial roles for seed health.

Distinct microbial communities associated with health-relevant wild berries

Lingonberries (Vaccinium vitis-idaea L.), rowanberries (Sorbus aucuparia L.) and rosehips (Rosa canina L.) positively affect human health due to their healing properties, determined by a high content of bioactive compounds. The consumption of unprocessed wild berries is relevant and encouraged, making their in-depth microbiological characterization essential for food safety. This study presents the first high-throughput sequencing analysis of bacterial and fungal communities distributed on the surface of lingonberries, rowanberries and rosehips. Significant plant-defined differences in the taxonomic composition of prokaryotic and eukaryotic microbiota were observed. The bacterial community on rosehips was shown to be prevalent by Enterobacteriaceae, lingonberries by Methylobacteriaceae and rowanberries by Sphingomonadaceae representatives. Among the fungal microbiota, Dothioraceae dominated on rosehips and Exobasidiaceae on lingonberries; meanwhile, rowanberries were inhabited by a similar level of a broad spectrum of fungal families. Cultivable yeast profiling revealed that lingonberries were distinguished by the lowest amount and most distinct yeast populations. Potentially pathogenic to humans or plants, as well as beneficial and relevant biocontrol microorganisms, were identified on tested berries. The combination of metagenomics and a cultivation-based approach highlighted the wild berries-associated microbial communities and contributed to uncovering their potential in plant health, food and human safety.

The analgesic and gastroprotective activities of the three fungal extracts and their possible correlation with the inhibition of the P2X7 receptor

P2X7 is a purinergic receptor physiologically activated by extracellular ATP. Its activation induces proinflammatory responses, including cytokine release, reactive oxygen species formation, and cell death. Previous in vivo experimental models demonstrated that P2X7 blockade has anti-inflammatory effects; however, there are no drugs used in clinical therapy that act on the P2X7 receptor. In the context of inflammatory diseases, nonsteroidal anti-inflammatory drugs (NSAIDs) are widely used as the first-line treatment; however, their major side effects include stomach ulcer formation, which increases patient morbidity and mortality. Here, we analyzed for the first time the analgesic and gastroprotective activities of three fungal extracts that showed antagonistic effects on P2X7 in vitro. The Antarctic fungal extracts obtained from Vishniacozyma victoriae, Metschnikowia australis, and Ascomycota sp. were tested in animal models of acute pain and ethanol-induced ulceration. These three extracts reduced paw licking by approximately 50 %, which is related to pain behavior, and reduced the number of stomach ulcers 3-7 times compared with the control (70 % ethanol), making them more efficient than the lansoprazole, an NSAID drug, and Brilliant Blue G (BBG), a known P2X7 antagonist, which only halves the number of ulcers. Furthermore, the extracts also protected the gastric mucosa and significantly reduced the levels of liver and renal enzymes compared with those in the ethanol group. Taken together, the fungal extracts presented both analgesic and possibly anti-inflammatory activities and had a protective effect on the gastric epithelium.

Identification and evaluation of an endophytic antagonistic yeast for the control of gray mold (Botrytis cinerea) in apple and mechanisms of action

Gray mold, caused by Botrytis cinerea, is a prevalent postharvest disease of apple that limits their shelf life, resulting in significant economic losses. The use of antagonistic microorganisms has been shown to be an effective approach for managing postharvest diseases of fruit. In the present study, an endophytic yeast strain PGY-2 was isolated from apples and evaluated for its biocontrol efficacy against gray mold and its mechanisms of action. Results indicated that strain PGY-2, identified as Bullera alba, reduced the occurrence of gray mold on apples and significantly inhibited lesion development in pathogen-inoculated wounds. Gray mold control increased with the use of increasing concentrations of PGY-2, with the best disease control observed at 108 cells/mL. Notably, Bullera alba PGY-2 did not inhibit the growth of Botrytis cinerea in vitro indicating that the yeast antagonist did not produce antimicrobial compounds. The rapid colonization and stable population of PGY-2 in apple wounds at 4 °C and 25 °C confirmed its ability to compete with pathogens for nutrients and space. PGY-2 also had a strong ability to form a biofilm and enhanced the activity of multiple defense-related enzymes (POD, PPO, APX, SOD, PAL) in host tissues. Our study is the first time to report the use of Bullera alba PGY-2 as a biocontrol agent for postharvest diseases of apple and provide evidence that Bullera alba PGY-2 represents an endophytic antagonistic yeast with promising biocontrol potential and alternative to the use of synthetic, chemical fungicides for the control of postharvest gray mold in apples.

Microbial Community Structure and Metabolic Function in the Venom Glands of the Predatory Stink Bug, Picromerus lewisi (Hemiptera: Pentatomidae)

The predatory stink bug, Picromerus lewisi (Hemiptera: Pentatomidae), is an important and valuable natural enemy of insect pests in their ecosystems. While insects are known to harbor symbiotic microorganisms, and these microbial symbionts play a crucial role in various aspects of the host's biology, there is a paucity of knowledge regarding the microbiota present in the venom glands of P. lewisi. This study investigated the venom glands of adult bugs using both traditional in vitro isolation and cultural methods, as well as Illumina high-throughput sequencing technology. Additionally, the carbon metabolism of the venom gland's microorganisms was analyzed using Biolog ECO metabolic phenotyping technology. The results showed 10 different culturable bacteria where the dominant ones were Enterococcus spp. and Lactococcus lactis. With high-throughput sequencing, the main bacterial phyla in the microbial community of the venom glands of P. lewisi were Proteobacteria (78.1%) and Firmicutes (20.3%), with the dominant bacterial genera being Wolbachia, Enterococcus, Serratia, and Lactococcus. At the fungal community level, Ascomycota accounted for the largest proportion (64.1%), followed by Basidiomycota (27.6%), with Vishniacozyma, Cladosporium, Papiliotrema, Penicillium, Fusarium, and Aspergillus as the most highly represented fungal genera. The bacterial and fungal community structure of the venom glands of P. lewisi exhibited high species richness and diversity, along with a strong metabolism of 22 carbon sources. Functional prediction indicated that the primary dominant function of P. lewisi venom-gland bacteria was metabolism. The dominant eco-functional groups of the fungal community included undefined saprotroph, fungal parasite-undefined saprotroph, unassigned, endophyte-plant pathogen, plant pathogen-soil saprotroph-wood saprotroph, animal pathogen-endophyte-plant pathogen-wood saprotroph, plant pathogen, and animal pathogen-endophyte-epiphyte-plant pathogen-undefined saprotroph. These results provide a comprehensive characterization of the venom-gland microbiota of P. lewisi and demonstrate the stability (over one week) of the microbial community within the venom glands. This study represents the first report on the characterization of microbial composition from the venom glands of captive-reared P. lewisi individuals. The insights gained from this study are invaluable for future investigations into P. lewisi's development and the possible interactions between P. lewisi's microbiota and some Lepidopteran pests.

Endophytic Bacteria and Fungi Associated with Polygonum cuspidatum in the Russian Far East

Polygonum cuspidatum, alternatively known as Fallopia japonica or Reynoutria japonica, is a perennial herb belonging to the Polygonaceae family. Commonly called Japanese knotweed or Asian knotweed, this plant is native to East Asia, particularly in regions such as Korea, China, and Japan. It has successfully adapted to a wide range of habitats, resulting in it being listed as a pest and invasive species in several countries in North America and Europe. This study focuses on analysing the composition of the bacterial and fungal endophytic communities associated with Japanese knotweed growing in the Russian Far East, employing next-generation sequencing (NGS) and a cultivation-based method (microbiological sowing). The NGS analysis showed that the dominant classes of endophytic bacteria were Alphaproteobacteria (28%) and Gammaproteobacteria (28%), Actinobacteria (20%), Bacteroidia (15%), and Bacilli (4%), and fungal classes were Agaricomycetes (40%), Dothideomycetes (24%), Leotiomycetes (10%), Tremellomycetes (9%), Pezizomycetes (5%), Sordariomycetes (3%), and Exobasidiomycetes (3%). The most common genera of endophytic bacteria were Burkholderia-Caballeronia-Parabukholderia, Sphingomonas, Hydrotalea, Methylobacterium-Metylorubrum, Cutibacterium, and Comamonadaceae, and genera of fungal endophytes were Marasmius, Tuber, Microcyclosporella, Schizothyrium, Alternaria, Parastagonospora, Vishniacozyma, and Cladosporium. The present data showed that the roots, leaves, and stems of P. cuspidatum have a greater number and diversity of endophytic bacteria and fungi compared to the flowers and seeds. Thus, the biodiversity of endophytic bacteria and fungi of P. cuspidatum was described and analysed for the first time in this study.

Comprehensive insights into the differences of fungal communities at taxonomic and functional levels in stony coral Acropora intermedia under a natural bleaching event

Previous studies have reported the correlations between bacterial communities and coral bleaching, but the knowledge of fungal roles in coral bleaching is still limited. In this study, the taxonomic and functional diversities of fungi in unbleached, partly bleached and bleached stony coral Acropora intermedia were investigated through the ITS-rRNA gene next-generation sequencing. An unexpected diversity of successfully classified fungi (a total of 167 fungal genera) was revealed in this study, and the partly bleached coral samples gained the highest fungal diversity, followed by bleached and unbleached coral samples. Among these fungi, 122 genera (nearly 73.2%) were rarely found in corals in previous studies, such as Calostoma and Morchella, which gave us a more comprehensive understanding of coral-associated fungi. Positively correlated fungal genera (Calostoma, Corticium, Derxomyces, Fusicolla, Penicillium and Vishniacozyma) and negative correlated fungal genera (Blastobotrys, Exophiala and Dacryopinax) with the coral bleaching were both detected. It was found that a series of fungal genera, dominant by Apiotrichum, a source of opportunistic infections, was significantly enriched; while another fungal group majoring in Fusicolla, a probiotic fungus, was distinctly depressed in the bleached coral. It was also noteworthy that the abundance of pathogenic fungi, including Fusarium, Didymella and Trichosporon showed a rising trend; while the saprotrophic fungi, including Tricladium, Botryotrichum and Scleropezicula demostrated a declining trend as the bleaching deteriorating. The rising of pathogenic fungi and the declining of saprotrophic fungi revealed the basic rules of fungal community transitions in the coral bleaching, but the mechanism of coral-associated fungal interactions still lacks further investigation. Overall, this is an investigation focused on the differences of fungal communities at taxonomic and functional levels in stony coral A. intermedia under different bleaching statuses, which provides a better comprehension of the correlations between fungal communities and the coral bleaching.

Biocontrol potential of volatile organic compounds produced by Streptomyces corchorusii CG-G2 to strawberry anthracnose caused by Colletotrichum gloeosporioides

Colletotrichum gloeosporioides is a fungal disease of strawberry fruit. Biocontrol strategies holds tremendous promise in alleviating fruit decay. Here, 30 actinomycetes were isolated from rhizosphere soil of Calotropis gigantea. A strain labeled with CG-G2 exhibited the strongest antagonistic activity against C. gloeosporioides and was assigned as Streptomyces corchorusii. Compared to strain CG-G2 extracts, the volatile organic compounds (VOCs) had a high antifungal activity against anthracnose. These volatiles effectively inhibited mycelial growth and spore germination of C. gloeosporioides. The hyphal and conidial structure was severely destroyed. Metabolomics analysis revealed that VOCs inhibited C. gloeosporioides via inducing flavonoids metabolism contributing to antifungal activity. Three main antagonistic compounds in VOCs were identified as methyl 2-methyl butyrate, hexanenitrile and methyl 2-Ethyl hexanoate. Especially, methyl 2-methyl butyrate demonstrated a remarkable efficacy in inhibiting fruit decay and preserving fruit quality. Hence, S. corchorusii CG-G2 will be a potential biocontrol agent for controlling anthracnose on harvested fruits.

Eco-friendly managements and molecular mechanisms for improving postharvest quality and extending shelf life of kiwifruit: A review

Kiwifruit (Actinidia spp.) is a commercially important horticultural fruit crop worldwide. Kiwifruit contains numerous minerals, vitamins, and dietary phytochemicals, that not only responsible for the flavor but can also serve as adjuncts in the treatment of diabetes, digestive disorders, cardiovascular system, cancer and heart disease. However, fruit quality and shelf life affect consumer's acceptance and production chain. Understanding the methods of fruit storage preservation, as well as their biochemical, physiological, and molecular basis is essential. In recent years, eco-friendly (comprehensive and environmentally friendly) treatments such as hot water, ozone, chitosan, quercetin, and antifungal additive from biocontrol bacteria or yeast have been applied to improve postharvest fruit quality with longer shelf life. This review provides a comprehensive overview of the latest advancements in control measures, applications, and mechanisms related to water loss, chilling injury, and pathogen diseases in postharvest kiwifruit. Further studies should utilize genome editing techniques to enhance postharvest fruit quality and disease resistance through site-directed bio-manipulation of the kiwifruit genome.

The influence of low-temperature resistant lactic acid bacteria on the enhancement of quality and the microbial community in winter Jerusalem Artichoke (Helianthus tuberosus L.) silage on the Qinghai-Tibet Plateau

Jerusalem Artichoke (Helianthus tuberosus L.), an emerging "food and fodder" economic crop on the Qinghai-Tibet Plateau. To tackle problems such as incomplete fermentation and nutrient loss occurring during the low-temperature ensilage of Jerusalem Artichokes in the plateau's winter, this study inoculated two strains of low-temperature resistant lactic acid bacteria, Lactobacillus plantarum (GN02) and Lactobacillus brevis (XN25), along with their mixed components, into Jerusalem Artichoke silage material. We investigated how low-temperature resistant lactic acid bacteria enhance the quality of low-temperature silage fermentation for Jerusalem Artichokes and clarify its mutual feedback effect with microorganisms. Results indicated that inoculating low-temperature resistant lactic acid bacteria significantly reduces the potential of hydrogen and water-soluble carbohydrates content of silage, while increasing lactic acid and acetic acid levels, reducing propionic acid, and preserving additional dry matter. Inoculating the L. plantarum group during fermentation lowers pH and propionic acid levels, increases lactic acid content, and maintains a dry matter content similar to the original material. Bacterial community diversity exhibited more pronounced changes than fungal diversity, with inoculation having a minor effect on fungal community diversity. Within the bacteria, Lactobacillus remains consistently abundant (>85%) in the inoculated L. plantarum group. At the fungal phylum and genus levels, no significant changes were observed following fermentation, and dominant fungal genera in all groups did not differ significantly from those in the raw material. L. plantarum exhibited a positive correlation with lactic acid and negative correlations with pH and propionic acid. In summary, the inoculation of L. plantarum GN02 facilitated the fermentation process, preserved an acidic silage environment, and ensured high fermentation quality; it is a suitable inoculant for low-temperature silage in the Qinghai-Tibet Plateau.

Improved phyllosphere microbiome composition of tea plant with the application of small peptides in combination with rhamnolipid

BACKGROUND

Small peptides play a crucial role in plant growth and adaptation to the environment. Exogenous small peptides are often applied together with surfactants as foliar fertilizers, but the impact of small peptides and surfactants on the tea phyllosphere microbiome remains unknown.

RESULTS

In this study, we investigated the effects of small peptides and different surfactants on the tea phyllosphere microbiome using 16S and ITS sequencing. Our results showed that the use of small peptides reduced the bacterial diversity of the tea phyllosphere microbiome and increased the fungal diversity, while the use of surfactants influenced the diversity of bacteria and fungi. Furthermore, the addition of rhamnolipid to small peptides significantly improved the tea phyllosphere microbiome community structure, making beneficial microorganisms such as Pseudomonas, Chryseobacterium, Meyerozyma, and Vishniacozyma dominant populations.

CONCLUSION

Our study suggests that the combined use of small peptides and surfactants can significantly modify the tea phyllosphere microbiome community structure, particularly for beneficial microorganisms closely related to tea plant health. Thus, this preliminary study offers initial insights that could guide the application of small peptides and surfactants in agricultural production, particularly with respect to their potential for modulating the phyllosphere microbiome community in tea plant management.

Biocontrol Screening of Endophytes: Applications and Limitations

The considerable loss of crop productivity each year due to plant disease or pathogen invasion during pre- or post-harvest storage conditions is one of the most severe challenges to achieving the goals of food security for the rising global population. Although chemical pesticides severally affect the food quality and health of consumers, a large population relies on them for plant disease management. But currently, endophytes have been considered one of the most suitable biocontrol agents due to better colonization and acclimatization potential. However, a very limited number of endophytes have been used commercially as biocontrol agents. Isolation of endophytes and their screening to represent potential characteristics as biocontrol agents are considered challenging by different procedures. Through a web search using the keywords "endophytes as biocontrol agents" or "biocontrol mechanism of endophytes," we have succinctly summarised the isolation strategies and different in vitro and in vivo biocontrol screening methods of endophytic biocontrol agents in the present review. In this paper, biocontrol mechanisms of endophytes and their potential application in plant disease management have also been discussed. Furthermore, the registration and regulatory mechanism of the endophytic biocontrol agents are also covered.

Effect of peach trichome removal on post-harvest brown rot and on the fruit surface microbiome

Postharvest peaches undergo rapid soft ripening and are susceptible to fungal diseases, which often result in severe losses during storage. The peach epidermis contains trichomes that form a specific structure on the peach surface. However, the relationship between trichomes and postharvest disease and involved mechanisms has not been well studied. In this study, the removal of trichomes reduced the disease incidence of peach brown rot caused by Monilinia fructicola. Cryo-scanning electron microscope observations showed that the fungal hyphae were found attached to the surface of trichomes. The fungal and bacterial communities on the peach surface at 0 d and 6 d were obtained by amplicon sequencing technology. Fungal communities on the peach surface contained a total of 1089 amplicon sequence variants (ASVs), which were demarcated into eight fungal phyla, 25 classes, 66 orders, 137 families, and 228 genera. The bacterial communities contained 10,821 ASVs assigned to 25 phyla, 50 classes, 114 orders, 220 families, and 507 genera. Higher bacterial diversity than fungal diversity was recorded on the peach epidermis. Trichome removal changed the microbial diversity and community on the peach surface. Compared with peach epidermis samples, the peach epidermis excluded trichomes samples contained similar fungal alpha diversity but significantly lower bacterial diversity. Seventeen different fungal genera and twenty-eight different bacterial genera were identified between peach trichome and peach epidermis excluded trichomes samples. The fungal and bacterial diversity on the peach epidermis showed a decreasing trend during storage. Beta diversity analysis revealed that the microbial communities of the peach epidermis and trichomes show different change trends between 0 d and 6 d. Trichome removal decreased relative abundance of Monilinia spp. and increased relative abundance of potential yeast and bacterial biocontrol agents. This study suggested that trichomes might modulate the microbial communities on fruit surfaces, and trichome removal technology after harvest might be developed to control peach postharvest decay.