Abstract
Gray mold caused by the necrotrophic fungus Botrytis cinerea is one of the major postharvest diseases of apple fruit. The exogenous application of 1-methylcyclopropene (1-MCP) and gaseous ozone (O 3) is commonly used to ensure postharvest fruit quality. However, the effect of these treatments on the susceptibility of apple fruit to postharvest pathogens remains largely unknown. Herein, the effect of O 3 and 1-MCP treatments on the development of gray mold on apple fruit (cv. “Granny Smith”) was investigated. Artificially inoculated apple fruits, treated or not with 1-MCP, were subjected for 2 months to cold storage [0°C, relative humidity (RH) 95%] either in an O3-enriched atmosphere or in a conventional cold chamber. Minor differences between 1-MCP-treated and control fruits were found in terms of disease expression; however, exposure to ozone resulted in a decrease of disease severity by more than 50% compared with 1-MCP-treated and untreated fruits. Proteomic analysis was conducted to determine proteome changes in the mesocarp tissue of control and 1-MCP- or O3-treated fruits in the absence or in the presence of inoculation with B. cinerea. In the non-inoculated fruits, 26 proteins were affected by 1-MCP, while 51 proteins were altered by ozone. Dynamic changes in fruit proteome were also observed in response to B. cinerea. In O3-treated fruits, a significant number of disease/defense-related proteins were increased in comparison with control fruit. Among these proteins, higher accumulation levels were observed for allergen, major allergen, ACC oxidase, putative NBS-LRR disease resistance protein, major latex protein (MLP)-like protein, or 2-Cys peroxiredoxin. In contrast, most of these proteins were down-accumulated in 1-MCP-treated fruits that were challenged with B. cinerea. These results suggest that ozone exposure may contribute to the reduction of gray mold in apple fruits, while 1-MCP was not effective in affecting this disease. This is the first study deciphering differential regulations of apple fruit proteome upon B. cinerea infection and postharvest storage treatments, underlying aspects of host response related to the gray mold disease.
Highlights
Apple (Malus domestica Borkh) is one of the most popular fruit crops cultivated throughout the world, with more than 80,000,000 tonnes of annual production (FAO, 2018)
Measurements of fruit qualitative parameters on the harvest day revealed that mean solids content (SSC), titratable acidity (TA), and fruit firmness levels were of 12.2◦Brix, 0.76%, and 70.5 N, respectively (Figure 1)
Applications of ozone and especially 1-MCP have been widely distributed throughout the world as postharvest treatments to extend the storage period of apple
Summary
Apple (Malus domestica Borkh) is one of the most popular fruit crops cultivated throughout the world, with more than 80,000,000 tonnes of annual production (FAO, 2018). During the long period of storage, apples become susceptible to various biotic (fungi and bacteria deterioration) and abiotic factors (physiological disorders), which lead to great economic losses. Fungal pathogens play a predominant role in fruit postharvest decay. It is estimated that more than 90 fungal species may be agents of postharvest diseases on apple fruits, and some of them can cause devastating losses that can reach up to 25% (Jijakli and Lepoivre, 2004). Gray mold caused by the necrotrophic pathogen Botrytis cinerea is a major postharvest disease of apple fruits throughout the world (Konstantinou et al, 2011; Nybom et al, 2020). The disease symptoms appear on the infected fruits during storage. Symptoms consist in the appearance of light tan to dark brown lesions that are irregular in shape without well-defined margins between healthy and decayed tissues (Konstantinou et al, 2011; Nybom et al, 2020)
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