Abstract
Pieces of bark cut out from one-year-old mulberry shoots (Morus alba L) cv. “Ichinose” showed antifungal activity (AA). When the pieces were placed on potato-dextrose agar (PDA) seeded with conidiospores from Bipolaris leersiae and were incubated at 25C for 1-2 days, mycelium inhibition zone appeared around the pieces. Pieces less than 0.1mm in length, however, did not show AA. The pieces were kept in moist conditions at 5 to 35C for various hours before being placed on the spore-seeded PDA. The intensity of AA increased when the pieces were kept at lower temperatures (5 and 10C), and it decreased, after an initial increase, at higher temperatures (15, 20, 30 and 35C). These changes were more conspicuous in the upper part of the shoots than in the middle and lower parts, and they were inhibited by dip treatment of the pieces with latex. The change of AA was confined to a region within 3mm length from the cut surface when using cut shoots. The AA was not detected in pieces incubated with the spore-seeded PDA for less than 4hr, but it was detected in pieces maintained on PDA for more than 6hr. The highest activity was found in the piece incubated with PDA for 18-24hr. When the pieces were heated at a temperature of more than 50C for 10min, it took a longer time for the pieces to show AA. When exposed to a temperature of more than 60C for 10min, AA could not be detected at least until 36hr after the treatment.
