Both Penicillium expansum and Trichothecim roseum Infections Promote the Ripening of Apples and Release Specific Volatile Compounds

Blue mold and core rot caused by Penicillium expansum and Trichothecium roseum are major diseases of apple fruit in China; however, their differential aggressiveness in apples and effect on fruit postharvest physiology are unclear. The effects of colonization of apples cv. Red Delicious by both pathogens were compared to physiological parameters of ripening and release of volatile compounds (VOCs). P. expansum colonization showed increased aggressiveness compared to T. roesum colonization of apple fruits. P. expansum enhanced colonization occurred with differential higher ethylene production and respiratory rate evolution, lower membrane integrity and fruit firmness in correspondence with the colonization pattern of inoculated apples. Moreover, P. expansum caused lower contents of total soluble solid and titratable acid, and higher malondialdehyde compared with T. roesum colonization. While both pathogen infections enhanced VOCs release, compared with T. roseum inoculated apples, P. expansum inoculated apple showed a higher total VOCs production including alcohols, aldehydes and esters, being the C6 alcohols, aldehydes and esters amount. PLS-DA analysis indicated that hexanoic acid was the most important factor to distinguish the inoculated fruits from the controls. Interestingly, propyl acetate and hexyl benzoate, and undecylenic acid and hexadecane were only identified in the P. expansum and T. roseum inoculated fruits, respectively. Taken together, our findings indicate that both fungi inoculations promote apple fruit ripening and release specific VOCs; moreover, apple fruits are more susceptible to P. expansum colonization than T. roesum.