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ARS Home » Northeast Area » Kearneysville, West Virginia » Appalachian Fruit Research Laboratory » Innovative Fruit Production, Improvement, and Protection » Research » Publications at this Location » Publication #312275

Title: Transcriptional profiling of apple fruits in response to heat treatment: involvement of a defense response during P. expansum infection

Author
item Wisniewski, Michael
item SPADONI, ALICE - University Of Bologna, Italy
item GUIDARELLI, MICHAELA - University Of Bologna, Italy
item PHILLIPS, JOHN - Retired ARS Employee
item MARI, MARTA - University Of Bologna, Italy

Submitted to: Postharvest Biology and Technology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/15/2015
Publication Date: 2/15/2015
Publication URL: http://handle.nal.usda.gov/10113/60410
Citation: Wisniewski, M.E., Spadoni, A., Guidarelli, M., Phillips, J., Mari, M. 2015. Transcriptional profiling of apple fruits in response to heat treatment: involvement of a defense response during P. expansum infection. Postharvest Biology and Technology. 101:32-48.

Interpretive Summary: The majority of the postharvest rots of apples that appear during storage are caused by fungal infections established on the fruit during harvest and processing. Restrictions on the use of fungicides established by regulatory agencies in the European Union and other countries, and consumer demand for fruit with residues much lower than regulatory levels have increased the demand for organically grown fruit and stimulated research into alternative control measures. Among physical treatments applied to fruit to control postharvest pathogens, hot water treatment of harvested fruits and vegetables has emerged as a safe and effective technique, having both a direct effect on pathogen spores and in stimulating apples to defend themselves. Understanding which genes are associated with the defense response of apples that are stimulated by heat treatment could provide valuable information for utilizing this technology in an optimal and reliable manner. The present study conducted a comprehensive analysis of gene expression of the response of apple fruit to a hot water treatment. The results indicated a significant increase in the expression of Heat Shock related genes: a class of genes that help plants to adapt to high temperature stress. This indicates that apple fruit respond to the heat treatment in a programmed manner and that genes responsible for adapting the fruit to high temperatures also result in greater resistance to postharvest disease. This information provides a set of gene responses that can be used to formulate optimal time and temperature treatments for different apple cultivars and different fruit commodities.

Technical Abstract: Heat treatment of harvested fruit has been demonstrated to be an effective and safe approach for managing postharvest decay. In the present study, the effect of a hot water treatment (HT) (45 degrees C for 10 minutes) on the response of apple to blue mold infection was investigated. HT was applied to ‘Ultima Gala’ apples using two different methods. Wounded apples were: 1) inoculated with a P. expansum spore suspension and then heat-treated after 1, 4, and 24 hours (Inoc-HT); or 2) first heat-treated and then inoculated with a P. expansum spore suspension after 1, 4, and 24 hours (HT-Inoc). All treated/inoculated apples were stored at 20 degrees C for six days. Significant reductions in fruit rot incidence, up to 100 percent, were observed using the Inoc-HT protocol at 4 and 24 hours while a 30 percent reduction in blue mold incidence was found at 1 and 4 hours using the HT-Inoc method. In vitro experiments showed no evident lethal effect of HT at 45 degrees C for 10 minutes on the germination of P. expansum conidia, indicating that this pathogen has a high heat tolerance. In order to investigate the molecular mechanisms involved in fruit response to heat treatment, an apple microarray was used to conduct a global transcriptional analysis of gene expression in apple at 0, 15, 30 minutes, 1, 4, 8, and 24 hours after the heat treatment. The results provided evidence that at 1 and 4 hours after heating, HT apples had the highest number of differentially expressed genes. A significant up-regulation of Heat Shock Proteins, Heat Shock Cognate Protein, and Heat Shock Transcription Factors genes involved in thermotolerance were observed. This indicates that apple fruit respond to the heat treatment in a programmed manner and suggests that genes responsible for thermotolerance may also be involved in the induced resistance response.