Fungi in Rice Field Open Irrigation System: Ecological Implications and Biosecurity

Italy is the leading producer of rice in Europe, but this crop is increasingly threatened by many factors such as pathogens' resistance, pollution and climate change. To date, few works keep in consideration the ecological role that the open irrigation system can play in the dispersion of important opportunistic species, and if it is affected by agricultural management and environmental seasonal changing. This work carried out the mycological characterization of a rice field irrigation system located in Vistarino (Pavia, Lombardy, Italy). Three main sections of an irrigation system (canal, ditch and paddy) were sampled during the summer 2018 (irrigation season of the rice crop). Water samples processing underlined how the irrigation system is rich of fungal diversity (59 species isolated). In order of abundance, the canal samples are characterized by the dominance of Aspergillus, Cladosporium, Fusarium and Trichoderma genera, while the ditch samples by Alternaria, Cladosporium, Fusarium, and Penicillium genera, and the paddy samples by Alternaria, Cladosporium, Fusarium and Trichoderma genera. Results showed that the three environments are mycologically independent of each other: fungi do not exploit the irrigation system for their dispersion in paddy. Probably fungi prefer others dispersion systems such as air dispersion. This means that an open irrigation system is not to be considered as a continue system with free circulation of fungi. Indeed, each sector of the system appears characterized by a typical funga, which undergoes variations during the sampled season due to agricultural management and environmental conditions.