Effects of soaking seeds with Pseudomonas alcaliphila Ej2 on endophytic community of rice roots under salt stress

Abstract:

[Objective] To reveal the impact of soaking seeds with fermentation broth of Pseudomonas alcaliphila Ej2 on the diversity and structure of endophytic community in rice roots under salt stress. [Methods] The total DNA of the endophytic bacteria and fungi of the roots of Ningjing 61 was extracted, followed by high-throughput sequencing of the V5–V7 regions of the bacterial 16S rDNA gene and the ITS1–ITS2 of fungal ITS region. Thereby, the regulatory effects of soaking seeds with Ej2 on endophytic community of rice roots under salt stress were analyzed.[Results] Soaking seeds with Ej2 significantly improved the diversity, richness, and evenness of endophytic community of rice roots under salt stress. To be specific, it increased the number of phyla, classes, families, genera, and operational taxonomic units (OTUs, read number≥5) of the endophytic community. In addition, for bacteria, it raised the relative abundance of Bacteroidetes (by 45.97%) and Actinobacteria (by 9.55%), and lowered the relative abundance of Firmicutes (by 12.22%). As to fungi, it significantly decreased relative abundance of Ascomycota (by 17.96%) and significantly elevated the relative abundance of Mortierellomycota andOlpidiomycota. Among them, Olpidiomycota was only detected after seed soaking with Ej2. After seeding soaking with Ej2, the relative abundance of Pseudomonas,Allorhizobium, Flavobacterium, and Devosia rose, and that of Preussia, Schizothecium, Fusarium, Aspergillus, and Monosporascus decreased. Olpidium was identified only after seed soaking with Ej2. As for the bacterial species, the relative abundance of P.stutzeri, P.alcaliphila, unclassified Pseudomonas, unclassified Rhizobium, and uncultured Rhizobium was up-regulated, and that of Hydrogenophaga flava was decreased after seeding soaking with Ej2. In terms of the fungal species the relative abundance of P.terricola, Neocosmospora rubicola, Gibberella intricans, A.penicillioides and unclassified Fusarium was reduced after seeding soaking with Ej2. PICRUSt2 prediction suggested that seeding soaking with Ej2 increased the abundance of bacterial community involved in various metabolic pathways in rice roots under salt stress, and FUNGuild analysis indicated the increase in the abundance of fungi related to the metabolism of animal pathogenic fungi, mycorrhizal fungi, and endophytic fungi, and reduction in relative abundance of saprophytic fecal community, fungal saprophytes, and plant pathogens.[Conclusion]Soaking seeds with Pseudomonas can significantly increase the diversity of endophytic community of rice roots under salt stress, change the structure of dominant endophytic flora, and improve the microecological environment of rice roots.