Response of triticale and its native rhizobacterial community to inoculation with a consortium of Paenibacillus sp. Z15 and Pseudomonas sp. KR227.

Triticale (× Triticosecale Wittmack) is an amphiploid cereal combining the high yield of wheat and the stress tolerance of rye. It is widely cultivated in Europe, primarily for forage and fodder. One of the most environmentally-friendly methods of increasing crop productivity is the use of the so-called plant growth-promoting bacteria (PGPB) - beneficial microorganisms that offer a sustainable alternative to mineral fertilization by enhancing plant growth and nutrient acquisition. This study evaluated the effects of a bacterial consortium, composed of Paenibacillus sp. Z15 and Pseudomonas sp. KR227 and possessing PGPB traits, on triticale growth and its rhizosphere bacterial community. Field experiments were conducted under randomized block design, and rhizosphere samples were collected three weeks after the inoculation and at harvest. Biometric measurements, soil physicochemical properties, and 16 S rRNA gene sequencing (V3–V4 region) were performed. The consortium significantly increased shoot biomass (1719.25 ± 176.52 g vs. 1408 ± 40.31 g in control) and spike mass (987.25 ± 109.61 g vs. 803 ± 10.42 g) and markedly enhanced root biomass at harvest (17.48 g vs. 9.62 g). No significant changes were observed in soil physicochemical parameters or alpha and beta diversity indices. Statistical analyses suggested a decrease in the relative abundance of Acidobacteriota, particularly the Vicinamibacteria class and genus RB41 (Pyrinomonadaceae). These compositional shifts were potentially mediated by secondary metabolites, without compromising overall community diversity. The results highlight the growth-promoting potential of the PP consortium in triticale and suggest that PGPB might modulate native rhizobacterial communities, warranting further research into their ecological impacts.