Abstract
It has been reported that Alternaria kikuchiana TANAKA, causal agent of black spot disease of Japanese pears drived from variety Nijisseiki, produces host-specific toxin. In this experiment, the host-specific toxic substance was isolated from culture filtrate and mycelium of the fungus.
After growing the fungus in potato-decoction medium added 2% sucrose at 25 to 28°C for 18 days, crude toxin was extracted with both ethyl ether from dried mycelium and chloroform from culture filtrate adjusted to pH 3.2 with N/1 HCl. The toxin was purified from acid fraction of crude toxin with column chromatography (silica gel column). As the purified toxin showed single spot by thin layer chromatography, it was regarded as monosubstance.
The young leaves of variety Nijisseiki, susceptable pear, responced to the isolated host-specific toxin, but the young leaves of variety Chojuro, resistant pear, did not responce to it.
