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Diseases of Aquatic Organisms

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DAO 153:59-68 (2023)  -  DOI:

First report of Achlya bisexualis infection in captive-reared Endangered golden mahseer Tor putitora

Victoria Chanu Khangembam*, Dimpal Thakuria, Vinita Pant, Ritesh Shantilal Tandel, Bipin K. Vishwakarma, Nityanand Pandey, Amit Pande, Pramod Kumar Pandey

ICAR-Directorate of Coldwater Fisheries Research, Bhimtal, Uttarakhand-263136, India
*Corresponding author:

ABSTRACT: Achlya bisexualis is a notorious oomycete pathogen with the potential to cause emerging disease in fish farms. In this study, we report the first isolation of A. bisexualis from captive-reared golden mahseer Tor putitora, an Endangered fish species. The infected fish showed a cotton-like growth of mycelia at the site of infection. The mycelium when cultured on potato dextrose agar produced radially growing white hyphae. The hyphae were non-septate, and some of them carried matured zoosporangium with dense granular cytoplasmic contents. Spherical gemmae with stout stalks were also observed. All the isolates had 100% identity in internal transcribed spacer (ITS)-rDNA sequence and showed highest similarity to that of A. bisexualis. In molecular phylogeny, all the isolates formed a monophyletic group with A. bisexualis which was supported by a bootstrap value of 99%. Based on the molecular and morphological findings, all the isolates were confirmed as A. bisexualis. Further, the anti-oomycete effect of boric acid, a known antifungal agent, against the isolate was evaluated. The minimum inhibitory concentration and minimum fungicidal concentration were found to be 1.25 and >2.5 g l-1, respectively. Isolation of A. bisexualis from a new fish species indicates its possible occurrence in other unreported hosts. Considering its wide infectivity and the potential to cause disease in farmed fishes, its probable prevalence in a new environment and host needs to be closely monitored to prevent the spread of infection, if any, by adopting suitable control measures.

KEY WORDS: Oomycete · Saprolegniales · New host · Morphology · Molecular characterization · ITS-rDNA · Phylogenetic analysis · Antifungal sensitivity

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Cite this article as: Khangembam VC, Thakuria D, Pant V, Tandel RS and others (2023) First report of Achlya bisexualis infection in captive-reared Endangered golden mahseer Tor putitora. Dis Aquat Org 153:59-68.

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