Effect of long-term sugar beet cultivation on rhizosphere bacterial diversity, community structure and sugar yield of sugar beet

Understanding the sugar beet holobiont for sustainable agriculture

“…Reduced nitrogen cycle-related gene abundance in sugar beet was observed when using chemical fertilization, alone or in combination with manuring (Cardinale et al, 2020). An indication for reduced nitrogen fixation with a concurrent increase of nitrification and aerobic ammonia oxidation in sugar beet rhizospheres was also found in a long-term crop rotation field (Du et al, 2022a). Archaeal nitrification in the rhizosphere further positively correlates with increasing soil depth (Stevanato et al, 2016).…”

“…With the increasing length of the taproot, a vertical gradient of microbial diversity, increasing with depth, establishes alongside the fine roots under field conditions (Stevanato et al, 2016 ). Proteobacteria are enriched compared to bulk soil in pre-harvest taproot rhizospheres, Acidobacteria, Actinobacteria, Bacteroidetes , and Gemmatimonadetes were mentioned as codominant bacterial phyla (Houlden et al, 2008 ; Kusstatscher et al, 2019a ; Cardinale et al, 2020 ; Huang et al, 2020 ; Du et al, 2022a ). The fungal rhizosphere community of pre-harvest taproots is dominated by Guehomyces, Humicola, Mortierella, Plectosphaerella , and Vishniacozyma (Kusstatscher et al, 2019b ; Du et al, 2022b ), but is most likely less conserved than bacterial communities (Houlden et al, 2008 ).…”

“…This diversity increase however was attributable to potentially phytopathogenic species ( Acidobacteria, Alternaria, Fusarium, Cladosporium ) while beneficial genera ( Bacillus, Actinobacteria, Pseudomonas ) declined. The genera Sphingomonas, Haliangium, Gaiella , and Lysobacter were positively correlated, while Lysinibacillus and Sphingobacterium negatively correlated with sugar beet cropping time (Huang et al, 2020 ; Du et al, 2022a , b ). It appears that long-time rotation with other crops does not fully restore the negative effects on sugar beet biomass, health parameters, and yield as well as on the community shift in bacterial (Cui et al, 2022 ; Du et al, 2022a ) and fungal (Cui et al, 2022 ; Du et al, 2022b ) rhizosphere microbiome compared to sugar beets grown in virgin soil.…”

“…The genera Sphingomonas, Haliangium, Gaiella , and Lysobacter were positively correlated, while Lysinibacillus and Sphingobacterium negatively correlated with sugar beet cropping time (Huang et al, 2020 ; Du et al, 2022a , b ). It appears that long-time rotation with other crops does not fully restore the negative effects on sugar beet biomass, health parameters, and yield as well as on the community shift in bacterial (Cui et al, 2022 ; Du et al, 2022a ) and fungal (Cui et al, 2022 ; Du et al, 2022b ) rhizosphere microbiome compared to sugar beets grown in virgin soil. Strategies to re-establish the microbiome-related beneficial effects on plant growth found in virgin soil, while increasing the sustainability of the crop is a challenge of future sugar beet research.…”

“…These differences in rhizosphere bacteria may have implications for soil-borne disease pathogenesis: bacterial isolates extracted from sea beet roots contained on average fewer antagonists of fungal phytopathogens but displayed higher tolerance toward salt stress when compared to isolates from sugar beet (Zachow et al, 2014 ). Since bacterial alpha diversity is often positively correlated with pathogen tolerance (Berg et al, 2017 ; Du et al, 2022a ), the microbiome itself may also contribute to the resilience of the sea beet. In addition, the coastline as natural habitat itself may contain low pathogen pressure compared to osmotic pressure, which again may emphasize the reciprocal adaption of the host and its microbiome within its natural habitat.…”