Saprolegnia pathogen from Pengze crucian carp (Carassius auratus var. Pengze) eggs and its control with traditional Chinese herb

Abstract

In the present study, a pathogenic strain, JL, was isolated from Pengze crucian carp (Carassius auratus) eggs suffering from saprolegniosis. It was initially determined as Saprolegnia sp. strain JL. Saprolegnia species have been implicated for significant fungal contamination, involving both living and dead fish and their eggs. A phylogenetic tree was constructed using the maximum parsimony method. The tree shows that the JL strain was closely related to Saprolegnia parasitica isolate SAP171, isolated from Salmo trutta suffering from saprolegniasis in Laukaa, Finland. The minimum inhibitory concentration (MIC) of 20 Chinese herbs was screened. Pseudolarix kaempferi Gord. (Pinaceae) was the most effective in inhibiting growth of the bacteria and was chosen for further trial. Significant protective efficacy of 52.63% and 73.68% was obtained against the JL strain in Pengze crucian carp eggs at P. kaempferi concentrations of 12.5 mg/ml and 25.0 mg/ml, respectively.