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ARS Home » Southeast Area » Fort Pierce, Florida » U.S. Horticultural Research Laboratory » Citrus and Other Subtropical Products Research » Research » Publications at this Location » Publication #407823

Research Project: Determination of Flavor and Healthful Benefits of Florida-Grown Fruits and Vegetables and Development of Postharvest Treatments to Optimize Shelf Life an Quality for Their Fresh and Processed Products

Location: Citrus and Other Subtropical Products Research

Title: Application of thymol vapors to control postharvest decay caused by Penicillium digitatum and Lasiodiplodia theobromae in grapefruit

item OLMEDO, GABRIELA - Orise Fellow
item ZHANG, JIUXU - University Of Florida
item Zhao, Wei
item Mattia, Matthew
item Rosskopf, Erin
item RITENOUR, MARK - University Of Florida
item Plotto, Anne
item Bai, Jinhe

Submitted to: Foods
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/28/2023
Publication Date: 9/30/2023
Citation: Olmedo, G., Zhang, J., Zhao, W., Mattia, M.R., Rosskopf, E.N., Ritenour, M., Plotto, A., Bai, J. Application of Thymol Vapors to Control Postharvest Decay Caused by Penicillium digitatum and Lasiodiplodia theobromae in Grapefruit. Foods. 12:3637. 2023.

Interpretive Summary: Since 2005, Huanglongbing (HLB) has ravaged Florida's citrus, causing an 80-90% drop in production. Alongside this, Diplodia stem-end rot (SER) incidence has surged at both pre- and postharvest stages, worsened by HLB. With Japan, a major buyer of Florida grapefruit, deeming grapefruit SER a quarantine disease, managing the pathogenic Lasiodiplodia theobromae fungi and formulating efficient quarantine methods becomes crucial. We have innovated a technique utilizing natural thymol vapors to curb SER growth. This method also effectively combats green mold (GM), another primary postharvest grapefruit disease.

Technical Abstract: Two of the major postharvest diseases impacting grapefruit shelf life and marketability in the state of Florida (USA) are the occurrence of stem-end rot (SER) caused by Lasiodiplodia theobromae and green mold (GM) caused by Penicillium digitatum. To address these post-harvest pathogens, we investigated the efficacy of vapors of thymol, a natural compound found in essential oils of various plants and the primary constituent of thyme (Thymus vulgaris) oil, as a potential solution for management of L. theobromae and P. digitatum in vitro and in vivo. Thymol vapors at concentrations lower than 10 mg L-1 , significantly inhibited mycelial growth of both L. theobromae and P. digitatum, causing severe ultrastructural damage of P. digitatum conidia. In in vivo trials, the incidence of GM and SER and lesion area on inoculated grapefruit were significantly reduced after a 5-d exposure to 50 mg L-1 thymol vapors. In addition, in vitro and in vivo sporulation of P. digitatum was suppressed by thymol. Thymol vapors had no negative effect on fruit, neither introducing perceivable off-flavor nor weight loss. Our findings support the pursuit of further studies of this compound, which is recognized as safe for human health and the environment, as a promising strategy for grapefruit postharvest disease management.