First report of Fusarium solani species complex infection on mandarin and maltese in Tunisia and semi-quantitative analysis of mycotoxins production in vitro

Fusarium spp. are well known plant pathogens that cause wilt and rot in roots and seeds. This study is the first to report Fusarium infection in mandarins and maltese in Tunisia. Samples of these varieties with Fusarium infection symptoms were collected from 5 orchards in northern Tunisia, resulting in a list of 12 isolates. The pathogenicity test of Fusarium isolates on oranges proved three highly virulent strains (L1, L3, and K6), which were subsequently identified using the sequence of the internal transcribed spacer (ITS) region to belong to Fusarium solani species complex (FSSC). Qualitative analysis of the enzymatic activities of the pathogenic isolates showed the potential of strains L1. L3, and K6 to produce amylase and protease. The metabolic profiling enabled the putative identification (level 2) of several secondary metabolites. L1 predominantly produced depudecin, while L3 and K6 produced fonsecin and sambutoxin. Moreover, correlation analysis suggested no clear trend between pathogenicity and fonsecin and sambutoxin production, and a negative trend with depudecin. Therefore, further investigations are required to validate the production of these metabolites in planta and to assess their potential implications for citrus health and food safety.