Medicinal plant extracts and protein kinase C inhibitor suppress zoosporogenesis and impair motility of Phytophthora capsici zoospores

Abstract

The effects of water and acetone extracts from 100 medicinal plants growing in Bangladesh, along with a selective inhibitor of protein kinase C (PKC), chelerythrine chloride, were tested on zoosporogenesis (release of zoospores from the sporangia) and motility of Phytophthora capsici zoospores. Among 10 active crude acetone extracts, those from Psidium guajava and Nigella sativa (100 μg/ml) suppressed zoosporogenesis relative to the control (100% zoospore release) to 60 and 40% released, respectively and inhibited motility of 100% of the zoospores within 60 min of treatment. Chelerythrine chloride also suppressed zoosporogenesis (30% released) at 0.1 μg/ml and inhibited motility of 100% zoospores at 0.2 μg/ml within 60 minutes. Among water extracts of 100 medicinal plants, 56 impaired motility of zoospores in a dose- and time-dependent manner. Diluted (20-fold) water extracts of 10 plants including Ocinum gratissimum, Terminalia bohera, and Duranta plumeri inhibited motility and subsequently caused lysis of zoospores. As the inhibition of zoosporogenesis and zoospore motility limit the possibility of infection by the peronosporomycete phytopathogen, the inhibitory crude extracts of medicinal plants identified in this study should have great potential for practical use as biopesticides against P. capsici.