Microbial antagonists against postharvest plant pathogens

Postharvest disease management is vital to increase the quality and productivity of crops. As part of crop disease protection, people used different agrochemicals and agricultural practices to manage postharvest diseases. However, the widespread use of agrochemicals in pest and disease control has detrimental effects on consumer health, the environment, and fruit quality. To date, different approaches are being used to manage postharvest diseases. The use of microorganisms to control postharvest disease is becoming an eco-friendly and environmentally sounds approach. There are many known and reported biocontrol agents, including bacteria, fungi, and actinomycetes. Nevertheless, despite the abundance of publications on biocontrol agents, the use of biocontrol in sustainable agriculture requires substantial research, effective adoption, and comprehension of the interactions between plants, pathogens, and the environment. To accomplish this, this review made an effort to locate and summarize earlier publications on the function of microbial biocontrol agents against postharvest crop diseases. Additionally, this review aims to investigate biocontrol mechanisms, their modes of operation, potential future applications for bioagents, as well as difficulties encountered during the commercialization process. 1. Introduction The human diet should include fruits and vegetables since they provide critical elements such as vitamins and minerals as well as antioxidant and anticancer compounds [1]. Increasing consumer awareness about diet and its health effects as well as their concerns about the safety of fruits and pesticide residues, toxins, and pathogens resulted in a larger intake of fruits and vegetables [2]. Infections caused by postharvest pathogens are currently the biggest worries for food production systems. They significantly shorten the shelf life of fruits and vegetables and cause significant deterioration during their postharvest processing, distribution, and storage. Postharvest fruit and vegetable diseases continue to have a large negative impact on the global economy, with losses estimated to be 20% in industrialized countries and over 50% in areas with storage and transportation constraints [3,4]. Significant losses of fruits and vegetables occur both in the field and during storage due to fungal spoilage. Fungal diseases linked to high moisture, low pH, high nutrients, and inherent resistance to decay after harvest are to blame for the high-degree loss of fruits and vegetables [5]. In addition to quality and monetary losses, fruits contaminated with fungi such as Aspergillus, Alternaria, Fusarium, and Penicillium pose a major health concern due to the mycotoxins they produce, including aflatoxins, ochratoxins, alternariol, and fumonisin [6]. In the past, the main technique for preventing fungus-driven postharvest deterioration was to apply agrochemicals either before or after harvest [7]. Nevertheless, the development of new pathogen biotypes, the rise of pathogen resistance to many fungicides, the increase in fungicide residue levels in agricultural production, the lack of effective substitutes, the negative effects on the environment, and toxicological issues relating to human health have made the utilization of synthetic fungicides in postharvest disease prevention a major source of concern for people in the agricultural sector [8]. People are compelled to look for safe and environmentally friendly alternatives in order to control postharvest infections and decay as a result of the aforementioned issues. The employment of antagonistic microbes for biological control is a novel and alluring alternative among the several methods for preventing postharvest infection and decay brought on by pathogens [9,10]. In comparison to synthetic fungicides, the application of antagonistic microbes in the management of postharvest disease has several advantages. They are inherently less harmful than chemical pesticides. Moreover, it affects only the target pest in contrast to broad-spectrum conventional pesticides [11]. Yet, scientific evidence indicates that these advantages are not always realized. Since microbial pesticides are living organisms, their main drawbacks include their extremely high specificity against the target disease and pathogen, which may require the use of multiple microbial pesticides, and their frequently variable efficacy brought on by the influences of various biotic and abiotic factors [11]. A number of fungal and bacterial biocontrol agents were identified for commercial use [5]. More information is also available on the formulation, fermentation, handling, and storage of biocontrol antagonists [12]. Therefore, the goal of this review is to give a comprehensive understanding of postharvest biocontrol systems driven by microbial antagonists, along with the mechanisms of biocontrol, usage, and ways to increase efficacy. Thus, the purpose of this chapter is to give a brief review of the utilization of microbial antagonists as postharvest biocontrol agents while summarizing data on their mechanisms of action, methods of application, and current constraints against their usage. More?contents2. Postharvest Disease Development2.1. Postharvest Diseases Management2.2. Biological Control2.3. Sources of Microbial Antagonists 3. Mechanisms of Microbial Antagonism3.1. Struggle for Nutrients and Space3.2. Siderophore3.3. Enzymes That Degrade the Cell Wall3.4. Pathogen Suppression through Antibiotic Production3.5. Lytic Enzyme Production and Mycoparasitism3.6. Induction of Host Resistance3.7. Production of Volatile Compounds3.8. Biofilm Formation and Quorum Sensing 4. Application Methods of Biocontrol Agents4.1. Preharvest Application4.2. Postharvest Application 5. Biocontrol: Status, Challenges, and Prospects6. Concluding Remarks ? A table (see the original paper, below) summarizes microbial antagonists recovered from various sources and used as biocontrol agents for postharvest plant diseases. SourcesThe Exploitation of Microbial Antagonists against Postharvest Plant PathogensLamenew Fenta, Habtamu Mekonnen and Negash KabtimerMicroorganisms 2023, 11(4), 1044https://doi.org/10.3390/microorganisms11041044https://www.mdpi.com/2076-2607/11/4/1044 Nexy, by Agrauxine, is sold in Spain by DECCO, and is the first biofungicide registered in Spain for use in the postharvest of citrus, apples and pears. Nexy has shown significant efficacy against Botrytis cinerea, Penicillium sp. and Colletotrichum sp.