Increased knowledge about induced resistance as tool to improve fruit and vegetable postharvest

Includes a very interesting review about the mechanisms involved in the induced resistancePostharvest losses have been estimated at 5?25% in developed countries and 20?50% in developing countries, depending on the commodity, cultivar, and marketing and handling practices (64). Consequently, the reduction of food loss and food waste is a major societal, economic, nutritional, and environmental challenge worldwide. The FAO reported that 14% of all food produced around the world is lost, not including at the retail and consumption levels, where 17% is wasted (40). Food losses and Food wasteTechnically, food losses include what occurs from the grower to retail, whereas food waste begins with the retail market and ends in the consumer home. Food loss and waste can be caused by senescence, physiological breakdown, mechanical injury, enhanced ripening, simple water loss to compositional changes, and deterioration of the crop by decay organisms. The development of innovative, global cultivars with improved color, shape, or taste is of limited commercial value without proper storage conditions that provide improved resistance to postharvest decay. Moreover, the removal from the market or the limitations on the use of broad-spectrum synthetic fungicides have increased the incidence of decay-causing fungi previously considered minor pathogens on most crops (e.g., fungal pathogens in the genera Rhizopus, Mucor, Alternaria, Aspergillus, and Penicillium) (119). Limiting constraints to extending the storability of cropsWith the trend toward healthier and widely available supplies of fresh fruits and vegetables, an ability to suppress postharvest diseases has become one of the most important limiting constraints to extending the storability of crops. In response, research investigating induced resistance in stored produce has increased greatly in the past 25 years (Figure 1), which has led to the practical deployment of induced-resistance technologies as significant alternatives to synthetic fungicides to control postharvest diseases. The induction of host defenses in fruits and vegetables includes the application of exogenous physical, chemical, and biological technologies that cause physiological changes in the plant to increase defenses against rot-causing fungal pathogens. Importantly, induced resistance confers protection toward a broad spectrum of postharvest rot pathogens during storage and shelf life, which gives it a central role in integrated disease management strategies. Progress in the development of scientific tools (e.g., molecular biology, genomics, etc.) has allowed better biological process monitoring than in the previous decades (25). Holistic understanding of postharvest behaviour?This process monitoring has increased the holistic understanding of the postharvest quality of fresh fruits and vegetables, which is influenced by combinations of technologies applied before and during storage (e.g., growth regulators and fungicides) as well as storage temperatures, storage atmosphere, and pre- and postharvest packinghouse protocols. Consequently, holistic tools that can provide an integrated depiction of how a range of biotic and abiotic factors alter host resistance become central to the improvement of crop quality and consumer health (123). This review highlights how these tools have allowed the unraveling of effects of host maturity, ripening processes, and senescence on the mechanism of induced resistance to postharvest disease. Contents- Postharvest physiology of fruits and their susceptibility to postharvest pathogens- Physiological mechanisms of host resistance to pathogens during fruit ripening- Comparison of physiological conditions of fruit contributing to resistance induction in climacteric and non-climacteric fruits- Mechanisms of resistance induction in fruit: treatment targets and host responsese- Induced resistance by postharvest treatments- Induced resistance in non-climacteric fruits- Induced resistance in climacteric fruits ConclusionsInduced resistance in fruit and vegetable tissues is a tool to confer enhanced protection against postharvest decay during storage and shelf life. Application of diverse abiotic and biotic stimuli triggers physiological host responses, inducing accumulation of defense compounds that limit fungal growth, delaying fruit senescence, preserving the physiological youth of fruit for longer periods, and enhancing the plant's ability to defend itself from invading pathogens. Therefore, induced resistance can (a) offer a defense strategy against many plant pathogens that are difficult to control by single resistance genes; (b) result in specific mechanism(s) of activation of defense responses; (c) modulate mechanisms that are widely present in many fruit crops; (d) activate mechanisms in the fruits that are considered safe and may even increase the quality of the fruits through the increase of beneficial compounds (phenols with antioxidant activity); and (e) be active throughout plant?fruit development, opening possibilities for both pre- and postharvest disease control (123). We discussed optimal timings of induction of plant response to the different inducers. Harvested fruits and vegetables show a decline in responsiveness to resistance induction with the progression of ripening and senescence. Current research is focused on the discovery of new resistance inducers and understanding their mechanisms of action to apply them at the proper time. Future research should also examine atmospheric modifications that can induce resistance by influencing host physiology and ripening. The study of biochemical mechanisms involved in the host response will benefit from technological innovations to monitor gene expression. Future efforts should also try to understand the contribution of the microbial populations (as a microbiome) to the host and pathogen interactions and verify their possible effects in induced resistance and, if positive, optimize the timing of preharvest and postharvest applications. Increasing the implementation of induced-resistance technologies will reduce the application of synthetic pesticides, moving toward a desirable sustainable approach in plant production and protection. Summary points1 -?Induced resistance reduces disease incidence by postharvest fungal pathogens by modulating the progression of ripening and senescence and by limiting the pathogen's ability to invade plant tissue. 2 -?Induced resistance was observed in both climacteric and non-climacteric fruits. 3 -?The process of induced resistance in disease-susceptible fruit is most strongly observed in conditions that delay ripening. 4 -?The interaction of constitutive resistance with induced resistance creates a fulcrum against pathogenesis that is affected by the physiological stage of the fruit and its response. Future issues1 -?Research should search for new stimuli of diverse origins to trigger physiological host responses that keep the produce physiologically younger for longer with a higher accumulation of nutraceutical compounds. 2 -?Efforts should be driven to discover new resistance inducers as compounds that improve the quality of fruits and vegetables (e.g., biostimulants) and the understanding of their possible effects on postharvest diseases. 3 -?Efforts should be invested to better understand the effect of the resistance-inducing potential of microbial populations on the host?pathogen interactions as possible factors that modulate fruit resistance. 4 -?We should characterize new induced secondary metabolites in treated fruits and vegetables, as they may affect taste and nutritional quality. AbstractHarvested fruit and vegetables are perishable, subject to desiccation, show increased respiration during ripening, and are colonized by postharvest fungal pathogens. Induced resistance is a strategy to control diseases by eliciting biochemical processes in fruits and vegetables. This is accomplished by modulating the progress of ripening and senescence, which maintains the produce in a state of heightened resistance to decay-causing fungi. Utilization of induced resistance to protect produce has been improved by scientific tools that better characterize physiological changes in plants. Induced resistance slows the decline of innate immunity after harvest and increases the production of defensive responses that directly inhibit plant pathogens. This increase in defense response in fruits and vegetables contributes to higher amounts of phenols and antioxidant compounds, improving both the quality and appearance of the produce. This review summarizes mechanisms and treatments that induce resistance in harvested fruits and vegetables to suppress fungal colonization. Moreover, it highlights the importance of host maturity and stage of ripening as limiting conditions for the improved expression of induced-resistance processes. Picture is Fig. 1 of the original paper - Number of articles available through Scopus (accessed April 11, 2023) over the past 25 years using the search keywords of "induced resistance postharvest". Adapted from Romanazzi et al (123) SourceInduced Resistance in Fruit and Vegetables: A Host Physiological Response Limiting Postharvest Disease DevelopmentDov Prusky & Gianfranco RomanazziAnnual Review of Phytopathology, Vol. 61:279-300 (Volume publication date September 2023)First published as a Review in Advance on May 18, 2023https://doi.org/10.1146/annurev-phyto-021722-035135 https://www.annualreviews.org/doi/full/10.1146/annurev-phyto-021722-035135?fbclid=IwAR0spsi8aW81GbMKevCeWCsrJ5MOVH4bd9gCL1SwVO8vHKkWqquiEDftjT4_aem_AZJpmG9r8LXtqaSMZgqv1VqfN-IgwYC7vhg39pWjeDIyAWg2scViK4BC9WQ5f1ux4wQ