Pseudomonas gilva sp. nov., a Plant-Associated Bacterial Species with Growth-Promoting Traits and Partial Suppression of Peanut Southern Blight

A rhizosphere-derived bacterial isolate, GYB4201T, was subjected to taxonomic and functional characterization. The strain consisted of Gram-stain-negative, strictly aerobic rods and was positive for both catalase and oxidase activities. Core-genome phylogeny placed GYB4201T within the Pseudomonas putida group, in which it occupied an independent and well-supported branch. Pairwise ANI and dDDH values relative to the most closely related type strains were below the accepted species boundaries. Its phenotypic and chemotaxonomic profiles provided additional evidence for taxonomic distinction. The cellular fatty acid composition was dominated by C16:0, Summed Feature 8 and Summed Feature 3. Phosphatidylethanolamine, phosphatidylglycerol and diphosphatidylglycerol were the principal polar lipids, while ubiquinone-9 was the predominant respiratory quinone. Functional assays demonstrated phosphate and potassium solubilization, indole-3-acetic acid production, CAS-positive siderophore-related activity, and inhibitory activity against Sclerotium rolfsii. Pot experiments further showed that inoculation with GYB4201T reduced peanut southern blight severity and promoted peanut growth. Positive but non-significant trends were observed in several root architectural traits. These taxonomic and functional data support the recognition of GYB4201T as a novel species of the genus Pseudomonas, for which the name Pseudomonas gilva sp. nov. is proposed. The type strain is GYB4201T (=CFCC 17085T = ICMP 25013T).