Phylogenetic diversity and plant growth-promoting characteristics of endophytic Pantoea spp. in rice seeds

Abstract:

[Objective] The genus Pantoea comprises 26 species that are isolated from a multitude of environments. In this study, 146 strains of Pantoea isolated from rice seeds of 8 different rice genotypes were systematically analyzed to determine their phylogenetic status, diversity, distribution and functional characteristics. [Methods] First, surface of rice seeds was sterilized by ethanol-sodium hypochlorite, and then the surface sterilized seeds were ground into a powder to isolate endophytic bacteria using the standard dilution plating technique. Second, the strains were purified and 16S rRNA gene sequencing and analyzed. Finally, the isolated strains were tested for plant growth-promoting, such as phosphorus solubilization, indoacetic acid (IAA) and siderophore production, antagonistic and hemolysis. Simple sequence repeats molecular marker technology was used to study the genetic polymorphism in five different genotypes of rice, and some agronomic traits such as tiller numbers, plant height, plant weight and rice production were studied. [Results] In total 146 endogenous Pantoea strains were isolated from 8 different genotypes of rice seeds. Pantoea strains were classed to Pantoea dispersa, Pantoea agglomerans, Pantoea cypripedii and Pantoea brenneri based on 16S rRNA gene phylogenetic analysis. Among the 4 species, P. dispersa has the largest size of population and existed in all 8 rice seed samples. Then, 66 strains were selected to test the plant growth-promoting characteristics, 86.3% and 69.7% of the strains were found to have the ability to dissolve phosphorus and produce IAA. 7 strains had the ability to produce siderophore. None of the strains was antagonistic to fungal pathogen Fusarium moniliforme. Another 3 strains had hemolytic activity. Pantoea composition did not correlate with rice phylogeny and agronomic traits. [Conclusion] The species and composition of Pantoea were different in different rice seeds. The seeds could selectively accumulated Pantoea as endophytic bacteria, and most of the strains had growth-promoting characteristics.