Members of the Complex Causing Wilt Symptoms in Medical Cannabis in Israel, Italy, and North America Comprise a Polyphyletic Assemblage.

Members of the complex are ubiquitous soilborne fungal pathogens causing wilt diseases in various plant hosts. () f. sp. was first reported causing wilt disease in hemp in Italy in 1962. To date, Fusarium wilt continues to cause concern in industrial and medicinal cannabis cultivation worldwide. During a 3-year period (2018 to 2021), strains were isolated from medical cannabis plants () exhibiting wilt symptoms that were cultivated in numerous commercial farms in Israel. A diverse set of these strains was subjected to molecular phylogenetic analyses to assess their genetic diversity and to compare them with other f. sp. isolates included in prior studies. Maximum likelihood bootstrap analysis of a partial translation elongation factor () dataset, which included 24 f. sp. sequences, revealed that the 11 strains from Israel comprised five haplotypes. Two of the haplotypes from Israel were identical to isolates previously reported from British Columbia and California and British Columbia and Ontario. Overall, the 24 f. sp. sequences included 12 unique haplotypes. These were phylogenetically diverse, suggesting that pathogenicity to may have evolved independently within the complex. Pathogenicity tests of the Israeli strains were confirmed by Koch's postulates assays. Strains of the five different f. sp. haplotypes all caused wilt in cannabis seedlings but with varying levels of aggressiveness. The same isolates that originated from asymptomatic infected mother plants were found in wilted cuttings indicating that the pathogen can be spread via propagation material.