Within‐generational but not cross‐generational effects of host plant on <i>Myzus persicae</i> performance and preferences

Abstract Myzus persicae (Sulzer) (Hemiptera:Aphididae) aphids feed on a wide range of host plants but exhibit strong preferences for plants from some families, particularly Brassicaceae. Previous studies demonstrate local adaptation of M. persicae populations, where populations collected on a given host plant have increased performance on this host, highlighting the potential for plant preferences and fitness to shift through cross‐generational changes or rearing on different plants within generations. Endosymbionts living within aphid cells can have substantial impacts on aphid fitness and also influence host plant responses. Rickettsiella is a facultative endosymbiont that shows potential biocontrol applications due to its host fitness costs, but it is unclear if costs change when aphids are reared on different host plants across generations. In experiments with two M. persicae lines (one carrying a transinfection of Rickettsiella ) we show that maintenance for 15 generations on leaf discs of three different host plants (bok choy, clover and potato) had little effect on fitness when reciprocally tested on each host plant. Fitness was mainly influenced by the host plant used for testing compared with cross‐generational effects. In two‐choice Petri dish experiments involving bok choy and clover, maintenance for 15 generations on either plant had no effect on plant preferences, but aphids acclimated to clover shifted their preference towards clover. The transinfected endosymbiont Rickettsiella was stable in all lines, where its deleterious effects and body colour alterations were not dramatically modified by the host plant used for maintenance or testing. This study highlights the adaptability of M. persicae to diverse host plants, stable transinfected endosymbiont effects and the importance of within‐generational host plant effects for fitness, with implications for the use of endosymbionts for pest management.