Invitroscreening for the antifungal activity of some Egyptian plant extracts against the fish pathogenSaprolegnia parasitica

Abstract

Saprolegniasis which is caused mainly by Saprolegnia sp. is the main cause of the winter mass kills in northern freshwater fish farms in Egypt. Various treatment protocols were used to control it, but they are not favoured due to toxicity and cost of treatment; thus, the search for safer economic alternative is ongoing. In this study, 50/59 plant/plant parts methanolic extracts were screened for the possible anti-fungal activity against a locally isolated Saprolegnia parasitica strain by agar plate dilution method. The screening revealed a significant inhibition of S. parasitica produced by 8 plant extracts, in which the highest inhibition rate was produced by Cyperus esculentus rhizomes, and the least efficacy amongst them belonged to Juniperus phoenicea fruits. Afterwards, the minimum inhibitory concentration (MIC) by the macrodilution broth assay was performed for them, which revealed that C. esculentus and Carthamus tinctorius extracts were the most effective with concentration of 0.1 ppm while the least activity among the effective extracts belonged to Chenopodium murale, Ipomoea batatas and Luffa aegyptiaca (fruit rend) with concentration of 10 ppm. In the present study, it was concluded that the methanolic extracts of C. esculentus rhizomes, C. murale whole plant, C. tinctorius flowers, I. batatas leaves, J. phoenicea fruits, L. aegyptiaca leaves and fruit rend, and Ricinus communis leaves, showed high inhibitory action against Saprolegnia in low concentrations, which may lead to their future usage in the aquaculture application.