Screening of Actinomycetes from Turmeric (Curcuma longa L.) and Ginger (Zingiber officinale) Rhizosphere for Antifungal Activity

Aim: The present study was carried out to isolate actinomycetes from rhizospheric soil of Curcuma longa and Zingiber officinale and evaluate their antifungal potential.

Methods: Actinomycetes were isolated from the rhizosphere soil of two Zingiberaceae plants (Curcuma longa and Zingiber officinale), using four different culture media. Isolates were screened for antifungal activity using dual culture technique against two reference strains Colletotrichum coccodes (DSM 2492) and Alternaria pimpriana (DSM 62023). The most potent strain was identified based on 16S rRNA gene sequence and the bioactive components of the strain were identified using GC-MS chromatography.

Results: Fifteen strains of actinomycetes were isolated, SCA (starch casein agar) was found best for cultivation of actinomycetes. The 15 strains were grouped into three genera Norcadia 8(54%), Streptomyces 5(33%) and Janibacter 2(13%) based on morphological, biochemical and physiological identification. Among the 15 isolates 6(40%) strains showed activity against either of the test organisms, while 1(6.7%) was active against the both test organisms. Comparative analysis of the 16S rRNA gene sequences identified the potent isolates as Janibacter sp. strain RC18. GC-MS analysis revealed the presence of 20 compounds with 10 identified as potent antimicrobial metabolites.

Conclusion: This study has revealed that rhizosphere of ginger and turmeric harbours rare actinomycetes that are valuable tool for sustainable agriculture.