Relationships between Fusarium population structure, soil nutrient status and disease incidence in field-grown asparagus

Fusarium species cause important diseases in many crops. Lack of knowledge on how Fusarium species and strains interact with their environment hampers growth management strategies to control root diseases. A field experiment involving asparagus as host plant and three phosphorus fertilization levels was designed to examine the seasonal changes and ecological relationships between Fusarium populations and their soil and plant environments. Fusarium taxa were identified and assessed using PCR-denaturing gradient electrophoresis of the EF1-alpha gene. Resulting profiles were analyzed with respect to 17 ecological parameters measured during the three main asparagus phenological phases across a growing season. Multivariate statistical analysis showed that Fusarium population structure was strongly influenced by soil P level while seasonal variation was less important. A significant relationship between Fusarium population composition and Fusarium crown and root rot incidence was also found in September. Canonical analysis further revealed significant relationships between Fusarium population structure, and plant manganese and iron contents, soil dehydrogenase activity and soil calcium concentration. If higher Fusarium crown and root rot incidence is related to the Fusarium community structure, strategies to reduce the incidence in asparagus plantations may be found through manipulation of the soil fertility.