Differences among Cacopsylla melanoneura Förster (Homoptera: Psyllidae) insight from molecular markers

The psyllid Cacopsylla melanoneura (Föster) is one of the vectors of ‘Candidatus Phytoplasma mali’, the causal agent of apple proliferation disease (AP). In northern Italy, overwintering adults of C. melanoneura can be found both on apple (Malus domestica L.) and on hawthorn (Crataegus monogyna L.) from the end of January. Eggs are laid on the two host plants around March and the neanids complete their development at the end of April. Around mid-June the new generation adults move to shelter plants. Adults of the new generation can be found on conifers (especially Picea abies L.) at high altitudes from the end of the summer to the winter. The presence of AP phytoplasma was assessed by PCR in overwintering adults collected on the three host plants (apple, hawthorn and Norway spruce). The genetic variations among populations of C. melanoneura collected on the different host plants and in different localities were analyzed using microsatellites markers developed for C. melanoneura and COI sequences. ‘Candidatus Phytoplasma mali’ was found in most of C. melanoneura populations with differences in the percentage and titre. Data obtained from microsatellite analyses indicate differences among populations, which could explain the differences in the efficiency of acquisition and transmission of AP phytoplasma by the different populations.