Abstract
In this study, cicada larvae infected with entomopathogenic fungi were collected from Maha Sarakham Province in northeast Thailand. One strain of entomopathogenic fungi with cottony white cream colonies was isolated. Small subunit (SSU) rDNA, large subunit (LSU) rDNA, the elongation factor 1α (EF-1α) and the largest subunit of RNA polymerase II (rpb1) sequence analyses were used for identification of the isolate. A BLAST search in NCBI showed the sequence to be most similar to Cordyceps sp., Hirsutella sp.,Ophiocordyceps longissima and O. longissima for SSU rDNA, LSU rDNA, EF-1α and rpb1, respectively. This correlated well with evidence from neighbor-joining trees, based on SSU rDNA, LSU rDNA, EF-1α and rpb1. Therefore, the isolate was classified as an anamorph strain of Ophicordyceps and assigned as Ophiocordyceps longissima isolate Cod-MK1. The O. longissima isolate Cod-MK1 was found to grow best in HCGA medium, compared with six other synthetic media. Moreover, the isolate was shown to develop numerous synnemata (stroma-like stalks) and conidia, when cultured in the applied HCGA medium at 25 to 28°C for 60 to 90 days. The content of adenosine was observed only in the extract from dried mycelia at 31.68 mg/g. The content of cordycepin from dried mycelia was 335.65 mg/g; lower than those of the extract from dried stroma-like stalks (366.14 mg/g). Therefore, the induced culture from this study could be used for the production of adenosine and cordycepin in O. longissima isolate Cod-MK1. Key words: Ophiocordyceps sp., identification, culture medium, phylogenetic tree, adenosine, cordycepin.
Highlights
The genus Cordyceps is a group of entomopathogenic fungi that form fruiting bodies and live mainly on insects and other arthropods (Wu et al, 2011; Zhu et al, 2011)
The colony on potato dextrose agar (PDA) that developed from the inner tissue of cicada larvae grew to 20 mm in diameter under 25 to 28°C within 30 days and assigned as the Cod-MK1 isolate
A phylogenetic tree was generated from 14 aligned sequences with an equal character
Summary
The genus Cordyceps is a group of entomopathogenic fungi that form fruiting bodies and live mainly on insects and other arthropods (Wu et al, 2011; Zhu et al, 2011). Many Cordyceps species are parasites of the cicada larvae (Wang et al, 2012). The infection process begins when spores of the fungus geminate and invade the body of the cicada larvae. Consumption of nutrients by the fungal hyphae eventually results in the death of the host. The internal tissue of the cicada larvae becomes replaced by a mass of mycelium and is transformed into a sclerotium. The fruiting body was developed on the surface of the host (Webster, 1980)
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