1978 Volume 44 Issue 4 Pages 485-492
Cortex tissues of one-year-old shoots of mulberry cultivar Ichinose, were inoculated with spore suspension or myceria of Fusarium solani f. sp. mori. The shoots were incubated in a moist case for various periods. Ten cortex disks 7mm in diameter or 0.2g of cortex tissues were immersed in 1ml of acetone for 3hr. Antimicrobial activity (AA) of the acetone extracts was examined with 1) hole slide- 2) cup- 3) TLC- 4) Plate- method using spores of Bipolaris leersiae. The extracts from infected tissues of summer and winter shoots showed AA. But AA was not detected in the extracts from non-infected cortices. Heated (90C, 10min) spores could not induce the AA. It is more necessary than 102 spores per cm2 of cortex surface to induce the AA. The AA was found in the extracts from cortices of shoots which were incubated at temperature ranging from 5 to 30C after inoculation of the spore suspension. Browning occurred in the infected tissues of cortices at higher temperature than 20C and AA was recognized only in the extracts of browned parts. Although browning of tissues was not observed so clearly at 5 and 10C, AA was detected in the extracts from all of the infected tissues of cortices. AA was found in the extracts from both summer and winter shoots, but little AA could be detected in upper part of new shoots in June. Growth of pathogenic fungi and bacteria of mulberry or silkworm was inhibited by the extracts from corticies inoculated with F. solani f. sp. mori. The AA was induced in the cortices by the treatments with culture filtrates of 7 plant pathogenic fungi. Antimicrobial compounds (AC) were extracted from cortex tissues inoculated with F. solani f. sp. mori with methanol, acetone, ethyl acetate and ethyl ether, but could not be extracted with water, n-hexane, carbon tetracloride. The AC were stable for 1hr at 120C or more than 6 months at 20C. The AC were dialyzable. Rf values of the AC on the cilica gel G thin layer chromatograhy developed with ethyl ether were 0.20 and 0.63. From these results, it was concluded that the AC were phytoalexins of mulberry. Chemical stractures of the AC of Rf value 0.63 were determined and these new compounds were named as moracin A and B by M. Takasugi et al.