Preliminary study on the microbiota associated with Cimiciato hazelnuts

Cimiciato hazelnuts are inedible and unmarketable. This defect is caused by the feeding activity of various species of pentatomids. The cimiciato-defect in hazelnuts is characterized by the presence of dry and necrotic tissues on the kernel, alterations in the lipid composition profile, and an increased susceptibility to lipid oxidation. These factors affect the organoleptic parameters and shelf-life of the product. Insect biting into hazelnuts determines the release of enzymes associated to saliva that induce biotic responses in plant tissues and metabolism alterations in kernels. Moreover, microbial inoculation during the feeding process is a well-documented phenomenon, as in the case of Eremothecium coryli (Peglion) Kurtzman, the causal agent of kernel dry rot in hazelnuts. Our study aims to explore the microbiota associated with the cimiciato defect occurring in insect-bitten hazelnuts of the San Giovanni cultivar harvested in Teano (CE), Campania region. Fruits were externally sterilised, shelled and disinfected. Cimiciato and healthy hazelnuts were then placed onto potato dextrose agar (PDA) or PDA + 1% lactic acid and transferred to a growth chamber. Fungal and bacterial colonies were observed and counted, to assess their presence or absence in each tested fruit. Noteworthy, cimiciato hazelnuts showed a higher presence of fungi compared to healthy hazelnuts. In contrast to this, no significant differences were found for bacteria. Further studies will be required for the molecular and phenotypic characterization of cimiciato-associated microbes together with metabolomic analysis, to determine how they contribute to development of this defect.