We explored the seed-associated bacterial endophytic microbiome in seeds of the endemic holoparasitic species Cistanche armena from a saline and arid habitat in Armenia. A combination of culture-dependent and molecular techniques was employed for identifying the seed endomicrobiome (culturable and unculturable). From surface-sterilized seeds, 10 phyla, comprising 256 endophytic bacterial genera, were identified. Of the culturable strains, we also investigated the plant growth-promoting (PGP) traits. Most of the isolates were spore forming, halotolerant and alkaliphile Bacillus spp., indicating that the endophytic bacteria of C. armena seeds own traits related to the natural habitat of their host plant. Our results confirm that Bacillus species are common and dominated endophytes from plants growing on saline and arid soils. Pantoea spp. and Stenotrophomonas spp. are more favourable PGP endophytes in seeds of C. armena. The PGP traits of these bacteria, such as production of indole, a precursor of auxin, ACC-deaminase and organic acids have the potential to improve the tolerance of their host plants against the abiotic stresses present in their natural habitat. To the best of our knowledge, this is the first report concerning bacterial seed endophytes of the C. armena.

Salt marshes are highly dynamic, biologically diverse ecosystems with a broad range of ecological functions. We investigated the endophytic bacterial community of surface sterilized seeds of the holoparasitic Cistanche phelypaea growing in coastal salt marshes of the Iberian Peninsula in Portugal. C. phelypaea is the only representative of the genus Cistanche that was reported in such habitat. Using high-throughput sequencing methods, 23 bacterial phyla and 263 different OTUs on genus level were found. Bacterial strains belonging to phyla Proteobacteria and Actinobacteriota were dominating. Also some newly classified or undiscovered bacterial phyla, unclassified and unexplored taxonomic groups, symbiotic Archaea groups inhabited the C. phelypaea seeds. γ-Proteobacteria was the most diverse phylogenetic group. Sixty-three bacterial strains belonging to Bacilli, Actinomycetes, α-, γ- and β-Proteobacteria and unclassified bacteria were isolated. We also investigated the in vitro PGP traits and salt tolerance of the isolates. Among the Actinobacteria, Micromonospora spp. showed the most promising endophytes in the seeds. Taken together, the results indicated that the seeds were inhabited by halotolerant bacterial strains that may play a role in mitigating the adverse effects of salt stress on the host plant. In future research, these bacteria should be assessed as potential sources of novel and unique bioactive compounds or as novel bacterial species.

TWA Editorial - Deputy Editor Kristine Petrosyan spotlights the importance of understanding the main issues regarding the oil industry that are discussed in the media.

TWA Editorial - Deputy Editor Kristine Petrosyan discusses old school vs. new school in economic evaluation.