Fusarium asiaticum: An Emerging Pathogen Jeopardizing Postharvest Asparagus Spears

Asparagus spears are usually vulnerable to pathogenic micro-organisms. In this study, 217 pathogens were isolated from symptomatic asparagus, and one highly virulent fungus (designated EXAP-08) isolated from the rotted asparagus spears in cold storage was characterized in detail. Koch's postulates were checked through pathogenicity tests, indicating that EXAP-08 infection could cause reproducible rot symptoms similar to those observed on naturally infected asparagus spears, and the pathogenicity of EXAP-08 was also relatively higher than other Fusarium pathogens, especially at 4°C. Through morphological and molecular identification, EXAP-08 was characterized as Fusarium asiaticum. This identification was further confirmed by phylogenetic analysis with the Histone gene H3 of EXAP-08 and other Fusarium species. EXAP-08 also belongs to 3A-DON (3-acetyl-4-deoxynivalenol) chemo-type, and the mycotoxin was detected during the infection of plant, implying the potential risks of mycotoxin contamination in fresh crops infected by this pathogen. Thus, this emerging pathogen threatening edible safety of asparagus spears should deserve particular quarantine inspection in the future.