Abstract
Fungi associated with Swida controversa leaves infested by zonate leaf blight were investigated in relation to symptom development, detachment due to defoliation, and decomposition. Their antagonistic effects on the pathogenic fungus were then studied in dual cultures on a nutrient agar medium. Pathogenic fungus was exclusively isolated from zonate parts of infested live leaves. Both endophytic fungi that were frequent on uninfected parts and pathogenic fungus were isolated from rim parts of symptom. Detection frequency of endophytic fungi was lower in leaf disks from which pathogenic fungus were detected than in those that were not detected, suggesting that endophytic fungi were excluded from leaves as symptom development. In detached leaves, pathogenic fungus was exclusively isolated from zonate parts, and both endophytic fungi and pathogenic fungus from rim parts. On the other hand, saprophytic fungi increased and original endophytic fungi decreased in uninfected parts. These suggest that the colonization of symptom by saprophytic fungi was limited on detached leaves. Pathogenic fungus was not isolated from decomposing leaves but saprophytic fungi were frequent on both zonate and uninfected parts. Eighteen strains in 9 species isolated from leaves showed overgrowth, contact inhibition, or inhibition at distance against four strains of pathogenic fungus in dual culture tests. The antagonistic effects depended on the combination of species or strain of test fungi and strain of pathogenic fungus.
