Possible insect vectors of ‘Candidatus Phytoplasma asteris’ and ‘Ca. Phytoplasma pruni’-related strains in Lithuania

Abstract

Phytoplasma strains affiliated with groups 16SrI, 16SrIII, 16SrV and 16SrXII have been found in Lithuania, but their insect vectors in the country have not been determined. ‘Candidatus Phytoplasma asteris’ and ‘Ca. Phytoplasma pruni’-related phytoplasma strains were identified in five leafhopper species and three spittlebug species occurring in Lithuania. The occurrence in Lithuania of Anaceratagallia ribauti, reported as a vector of stolbur phytoplasma (‘Ca. Phytoplasma solani’, subgroup 16SrXII-A) elsewhere in Europe, provokes the question of whether this phytoplasma may be present but yet undetected in Lithuania. The finding of subgroup 16SrI-C strains in A. ribauti, Aphrodes sp., Macrosteles sexnotatus and Euscelis incisus; 16SrI-B strains-in Aphrophora alni, Aphrodes sp. and Cicadella viridis; 16SrIII-B strains-in A. ribauti; and 16SrIII-P-in Aphrodes sp. and E. incisus is consistent with the hypothesis that these leafhopper species are vectors of the respective phytoplasmas in Lithuania. Transmission trials were initiated based on these results. Results thus far have revealed that Lithuanian biotype of E. incisus is capable of vectoring subgroup 16SrI-C phytoplasma strains that are found in Lithuania. The presence of diverse phytoplasmas in three spittlebug species, Aphrophora alni, Lepyronia coleopterata and Philaenus spumarius, indicates that these xylem feeders actually ingested phloem sieve cell contents during feeding on phytoplasmainfected plants, bringing into focus the question of whether some of such xylem feeders might act as occasional vectors of phytoplasmas.