Durum wheat kernel contamination by mycotoxigenic fungi and mycotoxins as affected by soil tillage and fertilization management in a Mediterranean environment

The emergence of the black point of grains, associated with mycotoxigenic Alternaria species, is becoming a significant concern in wheat disease management, alongside the well-established Fusarium head blight. Agronomic practices, including fertilization and tillage, can impact the prevalence of species within the mycotoxigenic fungal population. This study aimed to assess, through a three-year on-field trial (2020–2022), the effects of soil tillage techniques (ploughing versus subsoiling, and spading) and fertilization methods (mineral-based versus compost-based) on the colonization of kernels by mycotoxigenic fungi and the contamination of mycotoxins in durum wheat in Central Italy. In 2020 and 2021, kernels that were harvested showed symptoms characterized by black points, whereas no such symptoms were observed in 2022. The three years’ predominant fungal species were A. alternata and A. infectoria, with sporadic occurrences of Fusarium species. Contamination by mycotoxins produced by the Alternaria complex was detected, while those produced by Fusarium spp. were below the limit of quantification. This discrepancy could be attributed to environmental conditions favorable to the infection and development of Alternaria species. The frequencies of Alternaria and black point symptoms were observed not to correlate, paralleled by a negative regression between Alternaria infection and mycotoxin accumulation. Mycotoxin frequencies correlated with soil carbon content following mineral fertilization, while A. alternata frequency showed a negative correlation with organic fertilization. The results confirm that Alternaria mycotoxin contamination in wheat kernels poses a potential food safety risk at the European level.