EFFECTS OF THE TRYPANOCIDAL AGENTS BERENIL AND PENTAMIDINE ON GROWTH,ENZYME-ACTIVITIES, AND POLYAMINE CONCENTRATIONS IN THE RICE BLAST PATHOGEN PYRICULARIA-ORYZAE AND ON POWDERY MILDEW INFECTION OF BARLEY SEEDLINGS

The effects of the trypanocidal agents Berenil and pentamidine on grow th and polyamine biosynthesis in the rice blast fungus Pyricularia ory zae were examined. Fungal growth was substantially reduced by as littl e as 0.02 mM pentamidine and 0.01 mM Berenil. These compounds also con trolled infection of barley seedlings by the powdery mildew fungus Ery siphe graminis f.sp. hordei, with 1 mM Berenil or pentamidine reducing infection by 80 and 85%, respectively. Although both compounds reduce d in vitro activity of S-adenosylmethionine decarboxylase (AdoMetDC), the effects of pentamidine were more pronounced. Neither inhibitor had any effect on the in vitro activities of omithine decarboxylase (ODC) and spermidine/spermine acetyltransferase (SSAT). In in vivo studies, neither Berenil nor pentamidine significantly altered the activities of AdoMetDC, ODC or SSAT. Curiously, however, exposure of P. oryzae to either compound resulted in greatly increased putrescine and cadaveri ne concentrations and a much reduced spermine concentration. The chang es in polyamine concentrations may be due, in part, to increased activ ity of polyamine oxidase in fungal tissue following treatment with Ber enil or pentamidine. (C) 1995 Academic Press, Inc.