Dataset: Method and timing of rhizobacteria inoculation to plant roots alters success and strength of aphid suppression

Insect pests cause substantial yield losses globally, necessitating novel pest control approaches beyond chemical pesticides. Rhizobacteria, beneficial root-associated bacteria, present a promising alternative by enhancing plant growth and defences against pests.

This study explored the use of sodium alginate encapsulation for precise inoculation of two rhizobacteria, Acidovorax radicis and Bacillus subtilis, to suppress aphid (Sitobion avenae) populations on barley (Hordeum vulgare). We optimized a method using 4mm diameter wet-matrix alginate beads for controlled bacterial delivery directly to plant roots.

Rhizobacteria inoculation via alginate beads at root emergence significantly reduced aphid reproductive output, outperforming seed soaking methods, with increased effects when plants were infested with a high initial density of aphids. This suggests the prolonged release from alginate beads led to more consistent bacterial establishment to enhance plant defence responses triggered by aphid feeding.

Alginate bead inoculation demonstrated effective long-term bacterial viability following storage at 4° C for eight months. Our findings highlight the potential of alginate bead-encapsulated rhizobacteria for reducing aphid populations on barley but emphasizing the need for precise inoculation timing and placement.

This approach offers a robust method for empirical research and practical agricultural application, paving the way for sustainable pest management strategies. Future work should focus on optimizing formulations and understanding plant-microbe interactions to enhance field efficacy.

Methods
This dataset includes results from experiments investigating the effects of root-inoculated bacteria on barley plants (Hordeum vulgare) and their interactions with aboveground aphid herbivores (Sitobion avenae). Two bacterial species, Acidovorax radicis N35 and Bacillus subtilis B171, were used, with a control treatment of 10mM MgCl2. Plants of two barley varieties (Barbarella and Firefoxx) were grown in Levington’s Advance F1 low nutrient compost. Bacterial cultures were prepared by growing on nutrient agar or broth, harvested, and resuspended at OD600=2.0. Barley seeds were surface-sterilized and inoculated either by soaking in bacterial solutions or embedding bacteria in alginate beads formed by dropping bacterial-alginate mixtures into CaCl2. 

Three fully-factorial experiments were conducted. The first compared seed soaking and bead inoculation methods on aphid numbers, measuring plant shoot and root length and aphid reproduction after two weeks. The second tested timing of bead inoculation relative to seed germination and aphid infestation, tracking aphid fecundity and adult survival over 30 days. The third experiment examined the effect of different initial aphid densities on plant growth and aphid population dynamics. All experiments were arranged in randomized complete block designs and conducted in glasshouse or controlled growth cabinet conditions.

This dataset provides detailed measurements of plant growth (shoot and root length), aphid reproduction and survival, offering insights into plant-microbe-insect interactions.