Does Alternaria mouldy core infection of apple favour mycotoxin accumulation?

PAVICICH, MARÍA AGUSTINA; NIELSEN, KRISTIAN FOG; DE BOEVRE, MARTHE; DE SAEGER, SARAH; PATRIARCA, ANDREA

Workshop; ICFM Workshop 2022; 2022

Apple fruits aresusceptible to fungal infection during pre- and post-harvest with consequent foodspoilage and economic losses. Alternaria is able to produce external lesions onfruits and is the main causal agent of mouldy core (MC), a disease whoseseverity increases during food storage. As MC usually goes unnoticed in thevisual inspection performed by industries, the risk of by-products’ contaminationwith Alternaria mycotoxins increases.The objective of this study was to evaluate the metabolic capacity andmycotoxins production of Alternaria strainsisolated from apple fruits in vitroand in vivo according to their sourceand under different environmental conditions. A total of 78 Alternaria isolates from external lesionsand MC were characterized by their invitro secondary metabolite production profiles, determined by ultra-highperformance chromatography (UPLC) coupled with UV detection and high-resolutionmass spectrometry (HRMS). Twenty-seven secondary metabolites produced by thisgenus were identified, many of which are known as mycotoxins. Differencesaccording to the isolate source were observed: those obtained from MC showedgreater metabolic capacity than those from external lesions. The mycotoxinproduction of 3 Alternaria strains withhigh metabolic capacity was evaluated invivo. These strains were inoculated on both the outside and inside of undamagedfruits, simulating retail (T=25 °C, one month) and storage (T=4 °C, 9 months)conditions. Quantification of alternariol (AOH), alternariol monomethyl ether(AME), tentoxin (TEN), tenuazonic acid (TeA), altenuene, altertoxin-I and -II(ATXs), and modified forms of AOH and AME was done using targeted UPLC-MS/MS. The3 isolates were able to produce all the  described mycotoxins and some modified formsunder retail and long-term cold storage conditions in the interior and theexterior of the fruit. Higher levels of AOH, AME, TeA, TEN and ATXs accumulatedwhen Alternaria strains colonized thecentre of the fruit at 25 °C. Long-term cold storage usually performedby processing industries did not prevent the accumulation of Alternaria toxins in apples. The study resultsimply a risk of the presence of Alternariamycotoxins in fruits, both for retail and destined to processing. Our study suggeststhe need to assess mycotoxins’ natural occurrence in apple fruits and the by-products.