Fusaric acid production by Fusarium oxysporum f.sp lilii and its role in the lily basal rot disease

Fusarium oxysporum f.sp. lilii (Fol), the causal agent of lily basal rot, produced fusaric acid (FA) in aseptic culture. This toxin induced phytotoxicity symptoms on in vitro-grown lily bulblets of two different cultivars: the Fol-susceptible cultivar was more sensitive to the toxin than the Fol-resistant cultivar. When cultured in the presence of FA, the Fol-susceptible cultivar showed a greater tendency to accumulate FA within its tissues than the Fol-resistant cultivar. The polyphenol oxidase activity of the bulblets was inhibited by 1 mmol L-1 FA in both the cultivars, while at lower FA concentrations the enzyme activity increased only in the Fol-susceptible cultivar Peroxidase showed a steady activity at the 1 mmol L-1 FA concentration in both the cultivars, while at lower FA dosages its activity increased. Within the Fol-infected in vivo tissues of both the lily cultivars, FA was detectable only in traces. The role of this toxin in the lily basal rot disease seems therefore to be of marginal importance.