Plant growth-promoting rhizobacteria differently influence crops growth and physiology depending on cultivar and rhizobacteria consortium’s composition

Authors: AYELO, PASCAL - Texas A&M University; Adesemoye, Anthony; XIONG, CAIXING - Texas A&M University; FADAMIRO, HENRY - Texas A&M University

Submitted to: Biologia
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/10/2024
Publication Date: 5/23/2024
Citation: Ayelo, P.M., Adesemoye, A.O., Xiong, C., Fadamiro, H.Y. 2024. Plant growth-promoting rhizobacteria differently influence crops growth and physiology depending on cultivar and rhizobacteria consortium’s composition. Biologia. https://doi.org/10.1007/s11756-024-01710-9.
DOI: https://doi.org/10.1007/s11756-024-01710-9

Interpretive Summary: The importance of a specific group of bacteria termed plant growth-promoting rhizobacteria (PGPR) in sustainable agriculture is expanding and using multiple strains together as a blend appears promising to improve efficacy. During this study, local bacteria were collected in Texas counties, identified with modern sequencing technology, tested for their effect to hinder pathogen growth, and multiple of the bacteria were combined in five different blends. The blends were evaluated for effect on the growth promotion of two cultivars of corn and cotton as well as the effect on transpiration and conductance in the crops. All five tested PGPR blends increased the length and weight of root and shoot of susceptible corn and cotton, four of the bacteria blends enhanced the growth of resistant corn cultivar while two increased the growth of resistant cotton cultivar. The treatments also affected plant transpiration and stomatal conductance. The findings indicate that careful formulation of PGPR belonging to different groups as blends can improve efficiency of PGPR, broaden efficacy to multiple crops, but efficacy may vary depending on crop cultivar.

Technical Abstract: Plant growth-promoting rhizobacteria (PGPR) play a key role in sustainable agriculture by enhancing crop growth and offering protection against pests. Recent studies have highlighted several advantages in using well-formulated PGPR blends that promote synergistic interactions over single strains. However, developing PGPR blends that are effective on multiple crop cultivars is challenging. Five PGPR blends were tested for broad-spectrum growth promotion efficacy by comparing their effectiveness in susceptible versus resistant cultivars of corn and cotton. Firstly, we isolated rhizosphere bacteria from corn, cotton and wheat grown in Texas to identify indigenous PGPR strains, and those with biological activity against fungal pathogens were used to formulate three PGPR blends, hereafter called TX1, TX2 and TX3. Thereafter, using two corn and two cotton cultivars of contrasting resistance levels to fungal pathogens, we compared the effectiveness of these three new PGPR blends to two previously reported blends (AU9 and AU8). In addition, the effect of the PGPR blends on the crops’ transpiration rate and stomatal conductance was evaluated. The newly identified PGPR strains belong to five bacteria taxonomic groups: Bacillus, Paenibacillus, Pantoea, Peribacillus and Priestia. All PGPR blends increased the length and weight of root and shoot of the susceptible cultivars. For the resistant cultivars, blends AU8, TX1, TX2 and TX3 enhanced at least one of the corn growth parameters, while only TX2 and TX3 increased growth of the cotton plants. Resistant corn plants treated with AU8, TX1, TX2 or TX3 blend, and resistant cotton plants treated with AU8 or TX3 blend showed increased transpiration rate and stomatal conductance compared with untreated plants, but no significant differences were observed for the susceptible cultivars. The findings indicate that the PGPR blends performed differently on the crop cultivars, showing better growth promotion efficacy in susceptible cultivars than in resistant cultivars. Only the TX2 and TX3 blends significantly increased the growth of all four cultivars, regardless of resistance levels, suggesting that these blends have a great potential to enhance the growth of a broad range of corn and cotton cultivars.