Ecological genetics of Italian peach-potato aphid (Myzus persicae) populations in relation to geography, dispersal and insecticide resistance as studied using microsatellite and resistance markers

1) Eight polymorphic microsatellites and two insecticide resistance markers (kdr and R81T) were used to investigate the population genetics and demography of resistance mechanisms in field populations of the peach-potato aphid, Myzus persicae (Sulzer), a global crop pest, in several areas of Italy, notably the north-east, to determine if these parameters are linked to population structuring resulting from insecticide selective sweeps. 2) Individuals collected directly from peach orchards (primary host) in the spring, especially after control failure revealed 90 microsatellite alleles, around a third of which were rare. 3) Many field populations deviated from Hardy-Weinberg expectations (HWE), in a few instances due to null alleles. FIS values were on average negative (heterozygote excess), whilst FST values (0.04-0.334) reflected moderate interpopulation gene flow, non-structured populations having an estimated higher level than insecticide-treated ones. Population assignment and Mantel testing showed a non-homogenous pattern with some populations isolated genetically. LD was detected in four of the microsatellites and both resistance markers. Contrasting FST patterns with resistance status supported the view that some populations were indeed structured. 4) Lastly, Neighbour joining trees revealed some populations to have similar insecticide resistance profiles, independent of geographic origin. 5) Overall, the findings mean that natural M. persicae populations, living within an intensively cultivated agro-ecosystem, bear the signature of such management in terms of population structuring and perhaps also, dynamics.