Characterization of novel rhizosphere bacteria isolated from Vanda tricolor Lindl. var. Suavis Orchids in Mount Merapi Indonesia

Vanda tricolor Lindl. var. Suavis is an orchid indigenous to Mount Merapi, Yogyakarta, Indonesia. Conservation efforts are necessary due to its diminishing presence in its natural habitat, which is caused by recurrent eruptions and exploitation by irresponsible parties. Ex situ conservation initiatives using in vitro culture propagation have been implemented; however, the growth of Vanda tricolor in acclimatization remains slow, as reflected by minimal increases in plant height, leaf length, leaf width, root length, and root diameter. Consequently, efforts to promote the development of Vanda tricolor must be implemented, especially using bacteria that are symbiotic with orchid roots. The obtained characterization data could assist in the future selection of bacteria that can promote the growth of Vanda tricolor orchids. This study aims to identify and characterize bacteria from the roots and rhizosphere of Vanda tricolor orchids. The results indicated that fourteen isolates were isolated, of which eight showed nitrogen fixation and nitrification capabilities. The isolates were identified as members of the genus Bacillus by 16S rRNA gene sequencing, including Bacillus cereus , Bacillus toyonensis , Bacillus paramycoides and Bacillus sp. Phylogenetic research revealed that these isolates grouped within the Bacillus cereus sensu lato complex, signifying significant genetic similarity and possible ecological functions in enhancing plant growth. The results indicate that Bacillus isolates from the Vanda tricolor rhizosphere have beneficial properties for bioinoculant production aimed at promoting orchid growth. Future research emphasizing physiological and genetic validation is essential to verify their working processes and enable safe application in orchid conservation efforts.