The adsorption carrier of Bacillus velezensis PZ-3: screening and effects on microbial diversity in the rhizosphere soil of maize

Abstract:

[Background] Carriers influences the effects and costs of microbial fertilizers. [Objective] To screen the vector with strong adsorption ability of Bacillus velezensis PZ-3. [Methods] We carried out adsorption experiments for B. velezensis PZ-3 with biochar, humic acid, biomass ash, organic fertilizer, mushroom bran, and rice husk powder as carriers. The carrier suitable for the target strain was screened by dilution coating-colony counting method, flow cytometry, and maize pot experiment. Then, we investigated the effects of the adsorbed target strain on the microbial diversity in the rhizosphere soil of maize. [Results] The best colonization effect was achieved in the rhizosphere soil of maize after the adsorption of the target strain by humic acid+mushroom bran. The abundance and number of the target strain in the rhizosphere soil of this treatment peaked at 1.28×10⁵ CFU/g, with a relative abundance of 59.15%, on day 7. Compared with the control (original soil), this treatment increased the plant height, stem diameter, and aboveground dry weight of maize by 28.51%, 19.05%, and 48.65%, respectively. Moreover, this treatment increased the relative abundance of Streptomyces and Pseudomonas (P<0.05) and reduced the relative abundance of Paeniclostridium, Lophotrichus, and Gibberella in the rhizosphere soil of maize. [Conclusion] Humic acid combined with mushroom bran had a strong ability to adsorb B. velezensis PZ-3. The combination significantly promoted the growth of maize, increased the relative abundance of plant growth-promoting strains, and reduced the relative abundance of plant pathogenic fungi in the rhizosphere soil of maize.