Community Diversity of Endophytic Bacteria in the Leaves and Roots of Pea Seedlings

Endophytic bacteria from pea (Pisum sativum L.) plants play important roles in regulating plant growth, health, and nutrition. To enhance the understanding of endophytic bacteria in peas, twenty pea cultivars, two chickpeas, and two broad bean cultivars were planted into artificial soils for 4 weeks. Leaves and roots were collected from plants and sterilized. Endophytic bacterial DNAs were isolated from sterilized materials (leaves, roots, and seeds) and used as templates to detect the bacterial diversity by amplifying the 16S V3-V4 region. The Remel Tryptose Soya Agar (TSA) medium, the aluminum sec-butoxide (ASb) medium, and the yeast extract mannitol agar (YMA) medium were used to isolate bacteria from sterilized leaves and roots, respectively. The plant growth-promoting (PGP) properties of these isolated bacteria, such as the solubilization of phosphorus and potassium and the production of Indole-3-acetic acid (IAA), 1-aminocyclopropane-1-carboxylic acid (ACC) deaminase, nitrogenase, pectinase, and cellulose, were studied in vitro. Bacterial isolates were processed for 16S rDNA gene sequencing and performed molecular identification by reconstruction of the phylogenetic tree using the neighborhood association approach in the software MEGA X. Results indicated that the majority of the bacterial communities were shared among leaves, roots, and seeds of pea plants. In both the leaves and roots of pea plants, the prominent phyla identified were Pseudomonadota, Bacteroidota, and Bacillota, with dominant genera such as Rhizobium, Bacteroides, Blautia, and Prevotella prevailing at the genus level. The samples from leaves and roots had unique dominant bacterial genera. In total, 48 endophytic bacteria strains were isolated from leaves and roots, of which 16 strains were from roots and 32 strains were from leaves. The majority of the isolates from leaves (78.13%) and roots (75%) had the ability to produce indole-3-acetic acid (IAA). Moreover, isolates from roots also had greater ability to produce 1-amino-cyclopropane-1-carboxylic acid (ACC) deaminase (81.25%) than those from leaves (62.5%). This study demonstrated the unique distribution of endophytes in leaves and roots of pea, which can have great potential in pea production.