Biology subjects

Stelmach, M.

Publications and source records attributed to Stelmach, M..

4 recordsLinked to original sources

bioRxiv2026

Novel but stable endosymbionts have contrasting effects on aphid dispersal and plant feeding damage in the cereal pest Diuraphis noxia

Endosymbiotic bacteria can affect many ecological attributes of their insect hosts, including (in herbivorous insects) how insects interact with plants where they feed. This raises the issue of whether deliberate endosymbiont introductions could be used to decrease crop damage caused by insect pests. Here we investigate how transinfecting Rickettsiella viridis and Regiella insecticola endosymbionts into a novel pest aphid host, the Russian wheat aphid (Diuraphis noxia), influences population growth, alate production, dispersal ability and crop damage. Both the Rickettsiella (originating from pea aphids) and Regiella (from green peach aphids) were stably maintained in their new host where they had contrasting effects. Rickettsiella increased the severity of aphid damage on wheat and barley, resulting in greater leaf loss, chlorotic streaking, and higher aphid populations, whereas Regiella reduced aphid population growth and the severity of feeding damage by aphids. Their effects on dispersal morphology also differed: Regiella had no detectable impact on alate incidence, while Rickettsiella consistently suppressed wing formation in small cages, and in larger mesocosms with multiple wheat plants this endosymbiont suppressed dispersal. Endosymbiont-mediated changes in feeding damage did not involve the main plant immune response pathways: transinfected and wild type aphids induced similar levels of jasmonic acid, jasmonic acid-isoleucine, and salicylic acid in plant tissues, even though these plant defenses were strongly activated during aphid feeding. Novel endosymbionts can therefore modulate the severity of plant feeding damage by aphids as well as influencing aphid dispersal. Potential applications in controlling pest D. noxia populations are discussed. Significance statementEndosymbiotic bacteria that live within insect cells can have wide-ranging effects on the reproduction and fitness of their insect hosts in different environments. In herbivorous insects this includes effects on host plant use. Here we test if novel endosymbionts in a pest aphid, the Russian wheat aphid, might be used to decrease crop damage and dispersal. We show that the damage caused to wheat and barley plants from aphid feeding is modulated by novel but stably transmitted introduced endosymbionts. One endosymbiont (Rickettsiella) increased the severity of damage but decreased aphid dispersal, while another (Regiella) decreased damage severity without impacting dispersal. These contrasting effects may be associated with changes in aphid population growth and wing formation but were not linked to key plant immune response pathways. We discuss implications of these findings for using endosymbionts in agricultural pest management. Classification: Applied Biological Sciences, microbiology

microbiology↗

bioRxiv2024

Spread of a single superclone drives insecticide resistance in Acyrthosiphon kondoi across an invasive range

Populations under similar selection pressures may adapt via parallel evolution or dispersal of advantageous alleles. Here, we investigated insecticide resistance in the invasive blue-green aphid, Acyrthosiphon kondoi, which reproduces clonally in Australia and has rapidly developed resistance across geographic locations. Using genomic, transcriptomic, and experimental approaches, we explored the evolutionary origins and molecular mechanisms of resistance. We developed the first nuclear genome assembly for A. kondoi (443.8 Mb, 28,405 annotated genes, BUSCO score 97.5%) and a partial mitochondrial assembly (11,598 bp). All resistant strains shared a common ancestor, supporting the spread of a resistant superclone lineage that is distinct from susceptible strains. Resistance was associated with over-expression of an esterase gene that was homologous to E4/FE4 esterases in other aphid pests that are linked to resistance. Functional experiments in Drosophila melanogaster confirmed a causal role of this E4- like esterase in resistance to organophosphates, carbamates, and pyrethroids. These findings highlight how clonal dispersal and insecticide overuse can transform local adaptation into a widespread pest management issue. Our results suggest a parallel macroevolutionary response to insecticide selection in A. kondoi and other aphid species at the gene family level, but with a distinct regulatory mechanism in A. kondoi. Given the rapid spread of the resistant superclone, alternative management strategies, including expanded chemical control options and enhanced biological control, are urgently needed to mitigate this growing pest problem.

evolutionary biology↗

bioRxiv2024

Endosymbionts impact ladybird predation rates of aphids in a temperature-dependent manner

Aphids are worldwide pests causing major economic losses to growers. Current management strategies rely heavily on pesticides, but some effective pesticides are being withdrawn and the efficiency of remaining pesticides is also decreasing as aphids build up resistance. Biological control using predators can provide a sustainable alternative to pesticides under some circumstances, while the deliberate introduction of facultative bacterial endosymbionts that induce host fitness costs and reduce plant virus transmission provides another potential future strategy to combat aphid pests. However, new control options should not be antagonistic, with the concern that the effectiveness of biocontrol might be altered by endosymbiont presence in hosts. We, therefore, tested if predation by two aphidophagous ladybirds, Adalia bipunctata and Harmonia conformis, on the green peach aphid, Myzus persicae, and the oat aphid, Rhopalosiphum padi, was affected by transinfected Rickettsiella viridis and both native and transinfected Regiella insecticola endosymbionts at different temperatures. The predation rate of aphids infected by either endosymbiont was higher at 14 {degrees} C than the rate for uninfected aphids of both species, but the opposite pattern was apparent at 20 {degrees}C and for one host-endosymbiont combination at 26 {degrees}C. Overall, the results showed that higher temperatures increased predation, while differences between intermediate and low temperatures were species-dependent. No transmission of endosymbionts from aphid to ladybird through predation was detected. These findings point to a lack of consistent effects of the investigated endosymbionts on predation rates in these major aphid pests. The temperature dependence of endosymbiont-predation interactions suggests that the impact of seasonal climate should be considered when assessing the potential of endosymbionts in a biological control setting. HIGHLIGHTS- Aphid endosymbiont effects on ladybird predation rates are temperature-dependent - Ladybird predation rate of aphids increases as temperature rises - Prey (aphid) endosymbionts are not transferred to predators (ladybirds)

ecology↗

bioRxiv2024

The endosymbiont Rickettsiella viridis increases the virulence of Diuraphis noxia but reduces alate frequency

Aphids are among the worlds most economically damaging pests and carry a diverse range of bacterial endosymbionts. There is increasing interest in exploring potential applications of natural and novel strains of endosymbionts in aphid control. One endosymbiont, Rickettsiella viridis, has a large fitness cost following transfer from its natural aphid host Acyrthosiphon pisum into a novel host aphid Myzus persicae. Here, we investigated host impacts after transferring the same Rickettsiella strain to an important cereal aphid, the Russian wheat aphid Diuraphis noxia. Rickettsiella in this host resulted in modest fitness effects, with a minor increase in heat tolerance and a decrease in development time at 25{degrees} C. The infection persisted in mixed caged populations under different temperatures. Surprisingly, Rickettsiella increased aphid virulence to wheat plants and to two non-crop hosts of D. noxia, barley grass and brome grass. This was evident from sharper decreases in leaf number and leaf area, as well as an increase in chlorotic streaking when plants were exposed to Rickettsiella-infected D. noxia. Rickettsiella also reduced the proportion of alates in aphids held in small cages and in larger mesocosms containing multiple wheat plants where short-distance dispersal of aphids was impacted. These results provide compelling evidence that Rickettsiella can affect virulence - the first case of an endosymbiont transfer directly influencing aphid virulence to host plants - and highlight the species-specific impacts of endosymbiont transfers on aphids which can involve multiple traits.

microbiology↗