Genetic diversity and pathogenicity of Fusarium and Neocosmospora associated with cultivated and wild Asparagus officinalis in The Netherlands

Abstract

Fusarium crown and root rot is one of the main threats to asparagus production worldwide. The aetiology of the disease, attributed to several species of Fusarium and Neocosmospora, has not been re-evaluated in the context of recent advances in Fusarium taxonomy, and relevant studies in The Netherlands are scarce and outdated. Asparagus officinalis plants and associated soil samples were assessed from 38 cultivated fields and one location where this plant naturally occurs in The Netherlands. A total of 164 specimens were obtained yielding 551 fungal strains. Fungal identification according to DNA sequencing and phylogenetic analyses based on fragments of the translation elongation factor 1-alpha (tef1) and the DNA-directed RNA polymerase II second largest subunit (rpb2) showed that these isolates belonged to 20 taxa (Fusarium acuminatum, F. annulatum, F. avenaceum, F. carminascens, F. celtidicola, F. clavus, F. cugenangense, F. culmorum, F. equiseti, F. flagelliforme, F. flocciferum, F. inflexum, F. nirenbergiae, F. odoratissimum, F. oxysporum, F. redolens, F. vanleeuwenii, Neocosmospora geoasparagicola, N. solani and N. stercicola), of which 11 species (Fusarium avenaceum, F. carminascens, F. celtidicola, F. clavus, F. cugenangense, F. flagelliforme, F. flocciferum, F. inflexum, F. odoratissimum, F. vanleeuwenii and N. stercicola) are first reports on A. officinalis. These results, and testing of Koch’s postulates on A. officinallis plantlets, showed that F. annulatum, F. culmorum, F. redolens, F. nirenbergiae and N. solani were the most prevalent and aggressive species. In contrast, although F. oxysporum is pathogenic to A. officinalis, it was among the least prevalent species encountered in this study.