Available online at www.sciencedirect.com Postharvest Biology and Technology 47 (2008) 1–9 Impact of low-level atmospheric ozone-enrichment on black spot and anthracnose rot of tomato fruit Nikos Tzortzakis, Ian Singleton, Jeremy Barnes ∗ Environmental and Molecular Plant Physiology, Institute for Research on the Environment and Sustainability, Biology Division, Devonshire Building, Newcastle University, Newcastle Upon Tyne NE1 7RU, UK Received 14 December 2006; accepted 5 June 2007 Abstract Tomato fruit (Lycopersicon esculentum L.) were exposed to ozone concentrations between 0.005 (control) and 5.0 mol mol -1 up to 13 days at 13 ◦ C, prior to, or following, inoculation by Alternaria alternata or Colletotrichum coccodes (causes of black spot and anthracnose, respectively). Low-level atmospheric ozone-enrichment resulted in a modest, but statistically significant, reduction in fungal lesion development; higher con- centrations of the gas resulting in greater effects. This finding implies concentration-specific impacts on fungal lesion development. A fluorescent lection assay revealed that the ozone-induced inhibition of visible lesion development was reflected in a similar reduction in fungal biomass below the fruit surface. Fungal spore production in vivo, was markedly reduced when fruit were stored in an ozone-enriched atmosphere. Higher concentrations/duration of exposure resulted in greater reduction in spore production, with considerable benefits resulting from exposure to low levels of ozone (i.e. below the 0.2 mol mol -1 European threshold used for the protection of human health). In vitro, effects of ozone on spore germination depended on concentration and duration of exposure. Studies performed on fungi exposed to ozone on Potato Dextrose Agar at 13 ◦ C and 95% relative humidity revealed no major effects on the growth of mycelia, implying the observed suppression of pathogen development was due in part to ozone-induced changes in fruit-pathogen interactions. © 2007 Elsevier B.V. All rights reserved. Keywords: Alternaria alternata; Colletotrichum coccodes; Lectin fluorescence assay; Ozone; Spoilage; Tomato fruit 1. Introduction Postharvest storage of naturally ripened tomato fruit (Lycop- ersicon esculentum L.) is limited by both fruit softening and disease development (Barkai-Golan et al., 1989). Indeed, fol- lowing harvest, tomato fruit appear less capable of fending-off attacks by opportunistic pathogens and are more prone to bruis- ing (a factor predisposing fruit to subsequent infection/decay) (Mahovic et al., 2002). Microbial spoilage is most commonly controlled by decontaminating fruit (by washing in the presence of chlorine- or bromine-based disinfectants) and/or modification of the storage and transit environment (i.e. fungicide applica- tion, relative humidity (RH) and temperature) (Snowdon, 1990). However, commercial losses remain significant, as current pro- cedures are ineffective (Spotts and Peters, 1980; Sapers, 1998). ∗ Corresponding author. Tel.: +44 191 246 4837. E-mail address: j.d.barnes@ncl.ac.uk (J. Barnes). Tomatoes, like other fresh produce, are covered by a complex mix of bacteria, fungi and yeasts, with microbial diversity being commodity-specific and strongly influenced by growing con- ditions/climate (Mislivec et al., 1987). Major fungal pathogens affecting postharvest storage and shelf-life of tomato include: Alternaria alternata (Fr.:Fr.) Keissl. f. sp. lycopersici; Botry- tis cinerea (Pers.: Fr.); Rhizopus stolonifer (Ehrenb.:Fr.) Vuill.; Fusarium oxysporum Schlechtend.:Fr. f. sp. radicis-lycopersici Jarvis & Shoemaker; Geotrichum candidum (Link ex Pers.); Colletotricum coccodes (Wallr.) Hughes; Phoma lycopersici (Cooke); Rhizoctonia solani (K˝ uhn); Cladosporium herbarum (Pers.) Link; Phoma destructiva (Plowr.) and Pseudomonas syringae pv. tomato (Okabe) can also be important (Snowdon, 1991; Battilani et al., 1996; Mahovic et al., 2002). The dis- eases that these pathogens cause are generally favoured by moist conditions and are difficult to eradicate for several rea- sons, not least the capacity of the fungi concerned to produce spores that are highly resistant to eradication measures (e.g. fungicides, environmental manipulations, decontamination pro- cedures). In the early part of the 20th century, heat treatment 0925-5214/$ – see front matter © 2007 Elsevier B.V. All rights reserved. doi:10.1016/j.postharvbio.2007.06.004