Wheat (Triticum aestivum) is one of the most economically important crops in the world. During the routine monitoring of wheat pest, the cereal leaf beetle (CLB, Oulema melanopus, Coleoptera, Chrysomelidae), in the Greater Poland region, it was observed that some leaves wounded by CLB also displayed brownish lesions with clear margins and yellow halo, disease symptoms resembling a bacterial infection. The aim of this study was therefore to investigate those symptoms to establish a causal agent of the disease. The identification based on the results of the Biolog’s Gen III system, 16S rRNA, and gyrB genes sequencing, revealed the presence of eight strains of Pantoea ananatis bacteria. Four strains were derived from wheat leaves (Ta024, Ta027, Ta030, Ta046), and four from the CLB’s oral secretion (OUC1, OUD2, OUF2, and OUG1). They shared the nucleotide identity ranging from 99 to 100% to P. ananatis strains deposited in the GenBank database. Additionally, the multi-locus sequence analysis (MLSA) of concatenated sequences of partial atpD, fusA, gyrB, rplB, and rpoB genes was performed. All P. ananatis strains isolated in Poland, grouped into one cluster supported with high bootstrap value. Pathogenicity tests performed on four varieties of wheat plants have identified P. ananatis strains as a causal agent of wheat disease. To our knowledge, this is the first report of P. ananatis affecting wheat plants.

Bacteria isolated from bioaerosols emitted by a clarifier in a wastewater treatment plant (Dobre Miasto, Kosyń, Poland) were analyzed. A total of 27 morphologically different bacterial colonies were isolated, and 14 strains antagonistic towards Fusarium culmorum in vitro were selected for analysis. Most of the analyzed bacteria did not increase the germination capacity or the height of wheat seedlings. The only exception was strain PSDM20 which was characterized by multiple plant growth–promoting properties, but also by the lowest metabolic activity and lowest substrate assimilation. Strain PSDM16 deteriorated the status of wheat seedlings. Bacterial strains PSDM3, PSDM6, PSDM10, PSDM13, PSDM14, PSDM17, and PSDM20 prevented the deterioration of the biometric parameters of wheat seedlings exposed to F. culmorum and F. graminearum. Strains PSDM3, PSDM6, PSDM10, and PSDM17 most effectively protected wheat seedlings against infections caused by the above pathogens. Strain PSDM6 produced indole acetic acid (IAA), and it significantly contributed to plant elongation. Correlations were not observed between the growth-promoting properties, metabolic activity, and fungistatic properties of the evaluated bacteria. Pseudomonas putida PSDM3, Proteus penneri PSDM6, Enterobacter hormaechei PSDM10, and Advenella sp. PSDM17 were most effective in limiting the spread of Fusarium spp. infections in spring wheat, and they can be used as biological fungicides. The results of this study indicate that bacteria isolated from non-agricultural ecosystems are capable of protecting and fertilizing crops. The growth-promoting properties of bacterial strains of the genus Proteus are comparable with those of the widely investigated Pseudomonas spp. strains.