Experimental and molecular evidence of Reptalus panzeri as a natural vector of bois noir

Abstract

Bois noir (BN) is an economically important grapevine yellows disease induced by the stolbur phytoplasma and principally vectored by the cixiid Hyalesthes obsoletus. This study addresses the involvement of other planthoppers and/or leafhoppers in BN epidemics in the South Banat district of northeastern Serbia, by performing transmission experiments and multilocus typing of stolbur phytoplasma isolates to determine the vector-related characteristics of the disease. Transmission trials were conducted with adults of two cixiid congeners, Reptalus panzeri and R.quinquecostatus, which were found to harbour stolbur phytoplasma in the vineyards under study. A molecular characterization of stolbur phytoplasma isolates was performed by sequence analysis and/or RFLP typing of the two housekeeping genes tuf and secY and the two membrane proteins stamp and vmp1. Transmission trials with naturally infected R.panzeri adults from either the BN-infected vineyards or maize redness (MR)-affected maize fields revealed a high stolbur phytoplasma transmission efficiency to grapevines. In contrast, experiments conducted with stolbur-positive R.quinquecostatus originating from BN-infected vineyards, provided no evidence for a vector role of this species. Seven stolbur phytoplasma genotypes, all of which were tuf-b types, were detected among the grapevine- and insect-associated field samples according to the tuf/secY/vmp1/stamp typing. STOLg was the genotype most frequently found in naturally infected grapevine (42%), as well as R.panzeri originating from the vineyards (85%) and maize fields (98%). The same genotype was found in all experimental plants inoculated by R.panzeri, confirming its vectorship of the disease.