Two Sphingomonas species modify the productivity and the susceptibility of Pisum sativum to pea aphid, Acyrthosiphon pisum

• Soil bacteria, host plant and aphid pest exhibit specific interactions. • Aphids influence the functionality of rhizospheric communities of plants. • Aphids affect the metabolism of inoculated plants by top-down effects. • A bottom-up effect of soil bacteria altering the aphid behavior and fecundity. Aphids are major pests of field crops, and their control still largely relies on chemical insecticides, which have significant ecological and health drawbacks. Recent studies suggest that plants, such as pea ( Pisum sativum ) can recruit beneficial bacteria in the rhizosphere potentially influencing their resilience to insect pests. However, the implications of this microbial recruitment in plant-insect interactions remain underexplored. In this study, we investigated how key rhizosphere bacteria of pea, including Rhizobium leguminosarum, S. sediminicola , and S. daechungensis , modulate pea-aphid ( Acyrthosiphon pisum ) interactions and affect plant productivity. We assessed both the bottom-up effects of individual and combined bacterial inoculations on plant health and aphid performance, and the top-down effects of aphid infestation on soil functionality. Our results demonstrate that inoculation with S. sediminicola and/or S. daechungensis significantly reduced aphid fecundity, while mitigating aphid-induced stress on pea plants, thereby supporting overall plant growth and productivity. Conversely, aphid infestation negatively impacted soil functionality, potentially disrupting beneficial microbial communities. These findings highlight the potential of targeted microbial recruitment as a sustainable approach to enhance plant productivity and resilience against aphid pests.