Multilocus typing of aster yellows phytoplasmas infecting lettuce withyellowing in Calabria, Italy

Lettuce is an important vegetable crop commercially produced in many countries and affected by several bacterial diseases. The presence of phytoplasmas in lettuce plants growing in open field in Calabria region (Southern Italy) and showing yellowing and leaf necrosis was detected by PCR assays with primers amplifying 16S rRNA gene sequence. The ‘Candidatus Phytoplasma asteris’ strain identified in the symptomatic samples was further amplified on amp, groEL, and leucine genes for its molecular characterization. This lettuce strain resulted scattered in the fields and was identified by RFLP analyses as 16SrI-B; a multigene characterization confirmed its ribosomal subgroup affiliation and the validity of these molecular markers for studying the geographic distribution of phytoplasma strains of this taxon.