Abstract
One-year old shoots of 7 species belonging to 4 genera of Moraceae including mulberry were cut off transversely at the middle part in March in a field, and xylem tissues at the cut ends on the trees were examined in June. All the trees tested showed a brown zone at the part near the cut surface, and acetone extracts from the brownish reaction zone showed antifungal activity against Bipolaris leersiae when tested by the cup method. Acetone extracts from healthy xylem tissues of the same shoots showed no antifungal activity. Cut surfaces of mulberry shoots were inoculated with spore suspension of Fusarium solani f. sp. mori in April. In July, the shoots were cut longitudinally and then new xylem tissue profiles were observed. Both the part near the cut surface as well as the upper part of the lateral shoot, which were several and 10cm respectively distant from the inoculated cut surface, were brownish. The acetone extracts from these two brownish reaction zones showed the antifungal activity; the activity of the former being weak while the later was strong. The hyphae of F. solani f. sp. mori ceased to grow at the part about 1cm above the brown zone near the lateral shoot. Xylem fragments (7×10mm) of one-year old shoots of 7 species of Moraceae sampled in March were treated with water or spore suspension of F. solani f. sp. mori, and incubated for 4 days at 20C. Acetone extracts from inoculated and non-inoculated fragments of all 7 species showed antifungal activity. These antifungal substances were separated into 1 to 3 spots on a TLC sillica gel plate when developed with ethyl ether. The developed TLC plates were sprayed with potato dextrose broth containing spores of B. leersiae and inhibition zones were then observed. The number of inhibition zones and Rf values were almost the same in plants of the same Moraceae genus.
