HERBICIDAL ACTIVITY OF DEALANYLASCAMYCIN, A NUCLEOSIDE ANTIBIOTIC

A strongly phytotoxic activity was detected on screening culture broth s of soil streptomyces strains for herbicidal compounds. The active pr inciple was isolated and identified as dealanylascamycin, an already d escribed nucleoside antibiotic affecting bacterial protein synthesis. This compound strongly inhibited growth and development of both plant seedlings in Petri dishes and whole plants in pre- and postemergence t ests, as well as the growth of cultured plant cells. Monocot and dicot species were similarly affected. The inhibition was more pronounced o n roots than on shoots, while the germination rate was only slightly r educed. A preliminary investigation on the herbicidal mode of action o f dealanylascamycin was carried out by studying its effects on respira tion and protein synthesis rates both in short- and in long-term exper iments. The former were performed on rice- and carrot-cultured cells b y monitoring oxygen consumption and radioactive amino acid incorporati on rates, the latter on barley or common cowpea seedlings by following oxygen consumption and alpha-amylase accumulation rates. While short- term exposure to antibiotic concentrations close to those causing seve re growth inhibition did not appear to affect the investigated paramet ers substantially, long-term treatment led to remarkable, though not d ramatic, effects. Such effects, as judged by comparison with those ind uced by cycloheximide and chloramphenicoI, could not be ascribed to a primary inhibition of plant-cell protein synthesis. (C) 1994 Academic Press, Inc.