Ozkan Kaya, Sinem Karakus
Pomegranate (Punica granatum L.) fruit is highly susceptible to postharvest grey mold caused by Botrytis cinerea, which develops during cold storage and causes substantial losses, while concern over fungicide residues and resistance has intensified the search for natural alternatives. The present study evaluated an essential-oil blend (EOB) composed of thymol, eugenol and 1,8-cineole, applied at three doses, for the control of B. cinerea on pomegranate husk during 28 days of cold storage, and combined decay assessment with headspace solid-phase microextraction-gas chromatography-mass spectrometry (HS-SPME-GC-MS) profiling of the husk volatilome to elucidate the relationship between disease suppression and volatile change. Decay was effectively controlled in a dose-dependent manner: incidence at day 28 decreased from 72.4% in the inoculated control to 11.7% at the highest dose, corresponding to a disease-control efficacy of up to 83.8%, and the onset of decay was progressively delayed from day 7 in the control to days 21 and 28 in the lower- and higher-dose treatments, respectively. Volatile profiling identified 67 compounds across seven chemical classes, of which 49 differed significantly among treatments. The higher EOB doses elicited a marked, threshold-type accumulation of defense-related aldehydes and C13-norisoprenoids, including the bioactive apocarotenoid β-ionone, whereas esters and acids increased in parallel with decay and terpenes declined over storage. Multivariate, hierarchical-clustering and co-occurrence-network analyses resolved the volatilome into two distinct branches: an ester-acid module associated with disease progression and a separate aldehyde-C13-norisoprenoid module associated with the treatment response. To our knowledge, this is the first report to characterize the pomegranate husk volatilome in relation to essential-oil-mediated control of B. cinerea. These observations, together with the known antifungal activity of the oil constituents and the recognized role of C6 and apocarotenoid volatiles in plant defense, suggest that the essential-oil blend controls pomegranate grey mold through a combination of direct antifungal activity and an induced host response, and support its use as a natural, residue-free component of integrated postharvest disease management.