Characterization of Isolates of Fusarium spp. Obtained from Asparagus in Spain.

Microbial analysis of asparagus plants (Asparagus officinalis) obtained from four nurseries in Spain in 2002 to 2003 indicated high frequencies of Fusarium proliferatum, F. oxysporum, and F. moniliforme in the rhizomes and storage roots. Out of 201 isolates of Fusarium obtained from nursery crowns and from plants sampled in nine established asparagus fields, the highest frequency of highly pathogenic isolates was observed from samples collected from fields, and included some extremely virulent isolates of F. solani. For isolates of low to moderate virulence, the percentage of those significantly (P = 0.01) associated with root dry weight loss was larger for F. proliferatum (53.8%) than for the other Fusarium species (10.3 to 23.1%). Random amplified polymorphic DNA (RAPD) analysis of 19 isolates of Fusarium spp. grouped all F. proliferatum and F. moniliforme isolates together and, in a second cluster, five of the eight isolates of F. oxysporum. Asparagus cultivars Verde-Morado and Dariana were the least susceptible of 11 cultivars commonly grown in Spain; isolates of F. solani and F. moniliforme proved highly virulent; and a significant interaction was observed among pathogen isolates and asparagus cultivars when representative pathogenic isolates of F. proliferatum, F. oxysporum, F. moniliforme, and F. solani were tested on those cultivars. Larger reductions in root dry weight were associated with F. proliferatum and F. solani than with F. oxysporum and F. moniliforme, and differences in root and stem dry weights among cultivars were significant.