Transinfections of the endosymbiont <i>Rickettsiella viridis</i> in different <i>Myzus persicae</i> (Hemiptera: Aphididae) clones show consistent deleterious effects and stable transmission

Endosymbionts are widespread in insects, including aphids, and can have multiple effects on insect host fitness, suggesting potential applications for endosymbiont-related pest control. A transinfection of the endosymbiont Rickettsiella viridis into a line of the novel host Myzus persicae has previously shown large deleterious effects on aphid fitness and rapid spread in caged aphid populations under a cool environment. Because host clones can significantly influence endosymbiont effects and fitness-related traits more generally, it is important to test endosymbiont effects across a range of genotypic backgrounds. Here, we developed four Rickettsiella transinfected lines in different M. persicae clones via hemolymph microinjection, including clones with relatively high pesticide resistance. All four lines exhibited consistent fitness costs, reflected in reductions in both fecundity and longevity and reduced heat tolerance, although the magnitude of these effects varied among clones. The lines also resulted in stable and similar shifts in body color, with infected aphids being darker in color, although clonal effects were again observed. Vertical transmission was stable in all clones, and Rickettsiella infection was also shown to be transmitted horizontally between aphid pairs within Petri dishes in each clone. These results demonstrate consistent transmission and deleterious fitness effects of Rickettsiella transinfections, while also highlighting genetic background effects.