Variations in rhizosphere soil dominant and pathogenic flora improve boron-efficient Beta vulgaris L. yield under boron deficit

Boron (B)-efficient sugarbeet can potentially adapt better to the B deficient soil environments, however the characteristics of root yield or quality and rhizosphere soil microbial dynamics associated with B-efficient beet roots are extremely understudied. This study aimed to clarify the root yield characteristics and rhizosphere microbial response of B-efficient sugarbeet variety under B deficiency. Pertinently, the findings of this study will contribute to the reduction of B resource consumption and cleaner production in sugarbeet planting management. The study utilized two sugarbeet varieties with different B utilization propensities and subjected them to normal and B deficient field conditions. Results demonstrated a reduction in the yield quality of both varieties under B deficiency, but the B-efficient variety exhibited a smaller reduction. Boron deficiency reduced the species richness and diversity of the rhizospheric microbial community, decreasing the relative abundance of Actinobacteriota, Acidobacteria, while increasing that of Proteobacteria, Chloroflexi and the pathogenic fungus Fusarium. The proportion of dominant bacterial was severely reduced in B-inefficient varieties (0.86%) compared to B-efficient varieties (0.14%). The efficient variety displayed higher species richness of rhizospheric soil fungi and a higher abundance and proportion of dominant flora, i.e., Bacillus and Actinobacteria, albeit lower abundance of the pathogenic fungi Mortierellomycota and Rhizoctonia. These advantages allowed B-efficient sugarbeet variety to maintain higher yield levels under B deficit. Overall, under B-deficient conditions, B-efficient variety of sugarbeet was less limited than B-inefficient one, and its rhizosphere microbial communities were more conducive to sugarbeet yield in terms of composition and function. Succinctly, this study revealed the advantages of rhizosphere soil microorganisms associated with B-efficient beet under B-deficient environments and provided the theoretical basis for reducing boron fertilizer application to protect the ecosystem and realize green and clean agricultural production, particularly of sugar beet.