Species Diversity in the Fusarium solani (Neocosmospora) Complex and Their Pathogenicity for Plants and Humans

Unveiling Fusaria mycoflora associated with natural occurrence of lisianthus wilt and stem rot in Central-highland Vietnam

Wilt and stem rot (WSR) is an emerging syndrome threatening cut lisianthus (Eustoma russellianum) production in Lam Dong province, Vietnam. The disease was observed in all 13 inspected commercial lisianthus greenhouses across major lisianthus cultivation areas in Lam Dong, including Da Lat, Lac Duong, Don Duong, and Duc Trong, with incidence increasing with plant age, ranging from 7.5 to 32.4%. Infected plants displayed stunting, wilting, stem rot and blight, and dieback, with predominance of wilt and stem rot. The disease showed polycyclic behavior, with symptoms shifting from random or scattered in young plants to clustered patterns after the initial flower cutting. Forty-one Fusaria-like fungal isolates recovered from diseased lisianthus plants were identified as Fusarium vanleeuwenii (28 isolates), Neocosmospora solani (11 isolates), and F. annulatum (2 isolates) based on morphological observations and phylogenetic analysis of the internal transcribed spacer (ITS) region and translation elongation factor 1-alpha (TEF-1α) genes. The composition of Fusaria species varied across sites, with F. vanleeuwenii being consistently present. Pathogenicity tests confirmed that isolates of F. vanleeuwenii Li-Fo9511, N. solani Li-Fs4311, and F. annulatum Li-Fp3051 caused typical stem rot in in-vitro assays. In-planta assays showed wilting in seedlings starting two weeks post-infection, with a remarkable increase in disease incidence and severity between five and six weeks, particularly for F. vanleeuwenii Li-Fo9511. The pathogens were re-isolated and morphologically confirmed, fulfilling Koch's postulates. This is the first report of F. vanleeuwenii, N. solani, and F. annulatum as pathogens of lisianthus WSR in Vietnam, highlighting the need for effective control strategies.

Trans-kingdom fungal pathogens infecting both plants and humans, and the problem of azole fungicide resistance

Azole antifungals are abundantly used in the environment and play an important role in managing fungal diseases in clinics. Due to the widespread use, azole resistance is an emerging global problem for all applications in several fungal species, including trans-kingdom pathogens, capable of infecting plants and humans. Azoles used in agriculture and clinics share the mode of action and facilitating cross-resistance development. The extensive use of azoles in the environment, e.g., for plant protection and wood preservation, contributes to the spread of resistant populations and challenges using these antifungals in medical treatments. The target of azoles is the cytochrome p450 lanosterol 14-α demethylase encoded by the CYP51 (called also as ERG11 in the case of yeasts) gene. Resistance mechanisms involve mainly the mutations in the coding region in the CYP51 gene, resulting in the inadequate binding of azoles to the encoded Cyp51 protein, or mutations in the promoter region causing overexpression of the protein. The World Health Organization (WHO) has issued the first fungal priority pathogens list (FPPL) to raise awareness of the risk of fungal infections and the increasingly rapid spread of antifungal resistance. Here, we review the main issues about the azole antifungal resistance of trans-kingdom pathogenic fungi with the ability to cause serious human infections and included in the WHO FPPL. Methods for the identification of these species and detection of resistance are summarized, highlighting the importance of these issues to apply the proper treatment.