The underground organ microbial complexes of moorland spotted orchid <i>Dactylorhiza maculata</i> (L.) Soó (Orchidaceae)

Abstract

This paper is focused on the first study of microbiota of a moderate climate orchid from Northern hemisphere-Moorland Spotted Orchid Dactylorhiza maculata (L.) Soó growing in its natural habitat. There have been obtained detailed data concerning bacterial communities from rhizosphere and inner tissues of young and old tubers. It was done using the biomarker analysis method where the markers were detected by gas chromatography-mass-spectrometry. It is shown that the number of bacterial genera and the bacteria amount (10 5-10 8 CFU per gram of dry weight) in D. maculata microbial complexes decreases from rhizosphere to old tuber to young. At the same time all three bacterial cenoses closely resemble each other in biodiversity. Their constant members are gg. Hyphomicrobium, Methylococcus, Nitrobacter, Pseudomonas and Sphingomonas (Proteobacteria), Bacillus and Clostridium (Firmicutes), Rhodococcus and Streptomyces (Actinobacteria). There were found differences peculiar to the taxonomic structure of each microbial complex. The rhizosphere is dominated by Actinobacteria while in inner tissues Proteobacteria are prevalent. The bacteria of gg. Ochrobactrum, Xanthomonas, Butyrivibrio, Corynebacterium, Mycobacterium, Propionibacterium, Sphingobacterium and specific iron reducers were shown to belong to rhizosphere community. Genera of Agrobacterium and Bifidobacterium were found only in the endophytic microbiota of the young tuber while g. Aeromonas is specific for endophytic microbiocenosis of the old tuber. Endophytic bacteria complexes of the tubers differ in structure too: more numerous and diverse Actinobacteria mark the old tuber while the young organ has bigger share of gg. Bacillus and Clostridium. The results suggest that the endophytic bacteria in tubers originate from rhizosphere. By means of plating on nutrient media there were isolated three phyla of bacteria-Proteobacteria, Firmicutes and Actinobacteria which made up 10 3 CFU per gram of fresh tissue weight. The phylum of Bacteroidetes, a minor part of the microbiocenosis was found only by biomarker method. The bacterial genera associated with D. maculata detected by us can positively influence the plant by means of their exometabolites. It can be used for strategic and tactical approaches to rare species conservation.

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