Influence of Chrysanthemum yellows phytoplasma on the fitness of two of its leafhopper vectors, Macrosteles quadripunctulatus and Euscelidius variegatus.

Chrysanthemum yellows phytoplasma (CY) is a strain of aster yellows, which is classified as 'Candidatus Phytoplasma asteris' (16 SrI-B). The amounts of CY cells as genome units per ng of insect DNA was measured in individuals oí Macrosteles quadripunctulatus (Kirschbaum) (Rhynchota Cicadellidae) and Euscelidius variegatus (Kirschbaum) (Rhynchota Cicadellidae), using PCR on total DNA followed by real-Time PCR. The effects of CY infection in terms of longevity and fecundity were also measured. CY was propagated in daisy (Chrysanthemum carinatum Schousboe) where the third and the fourth instar nymphs were fed. Healthy leafhoppers and those fed on daisy were maintained on oat (Avena sativa L.). After emergence as adults, individuals from populations of infected insects were assayed for CY presence. All the ten tested specimens of M. quadripunctulatus were found to carry CY at high titres (on average 70,000 cells per ng of insect DNA) whereas nine out of 10 E. variegatus sampled were infected at considerably lower levels (on average 3,700 cells per ng of insect DNA). Survival times of both male and female M. quadripunctulatus were reduced by CY infection but no significant effect was found with E. variegatus. CY infection of M. quadripunctulatus females did not affect their fecundity, whereas that of E. variegatus females was slightly increased.