Abstract
In this study, we isolated a total of 238 culturable putative bacterial endophytes from four Pinus species (Pinus densiflora, P. koraiensis, P. rigida, and P. thunbergii) across 18 sampling sites in Korea. The samples were cultured in de Man Rogosa Sharpe and humic acid-vitamin agar media. These selective media were used to isolate lactic acid bacteria and Actinobacteria, respectively. Analysis using 16S ribosomal DNA sequencing grouped the isolated putative bacterial endophytes into 107 operational taxonomic units (OTUs) belonging to 48 genera. Gamma-proteobacteria were the most abundant bacteria in each sampling site and three tissues (needle, stem and root). The highest OTU richness and diversity indices were observed in the roots, followed by stem and needle tissues. Total metabolites extracted from three isolates (two isolates of Escherichia coli and Serratia marcescens) showed significant nematicidal activity against the pine wood nematode (Bursaphelenchus xylophilus). Our findings demonstrated the potential use of bacterial endophytes from pine trees as alternative biocontrol agents against pine wood nematodes.
Highlights
Endophytes have received significant research interest and show great potential as biocontrol agents (BCAs)[1,2,3,4,5]
The analysis identified 116 endophytic isolates belonging to 74 operational taxonomic units (OTUs) and 26 genera (Supplementary Table S2)
Only 24 Actinobacteria corresponding to 12 OTUs were isolated
Summary
Endophytes have received significant research interest and show great potential as biocontrol agents (BCAs)[1,2,3,4,5]. Chemical methods for controlling plant parasitic nematodes have been extensively applied because of their non-selectivity. Despite their effectiveness and availability, chemical nematicides have been reconsidered due to the disadvantages, such as high risk for environmental hazard[10,19,20]. Www.nature.com/scientificreports from Streptomyces avermitilis, an Actinobacteria species, exhibits significant nematicidal activity[21]. We isolated large numbers of putative BEs that do not belong to Actinobacteria and LAB. We screened the isolated putative BEs for nematicidal activity against PWN. Screening results showed that Escherichia coli and Serratia marcescens exhibited significant nematicidal activity and can potentially be used as BCAs against PWN. We tested the hypothesis that the hosts may possess endophytes that can be a practical and effective choice as pest control agents
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