First Report of Phytoplasmas Associated with Erysimum linifolium L. Stunting

Erysimum linifolium L. (sin. Cheiranthus linifolium L.) (Brassicaceae), or Aegean wallflower, native to the Mediterranean region, is an evergreen perennial ornamental shrub cultivated in Liguria region (northern Italy) to be used in rock gardens or in mixed garden borders. In 2012, a phytoplasma-like disease was observed in a few pot-plants at an ornamental grower of Albenga area (Savona). Symptomatic E. linifolium showed reduced leaf size, rosetting and stunting; in some cases, shortening of internodes and growing reduction involved only a part of the plant. After first symptoms observation, an increasing percentage of symptomatic plants were found at flowering stage, when affected plants did not bloom. Samples from symptomatic and asymptomatic plants were collected and tested by direct PCR with primers P1A/P7A followed by nested-PCR with primers F1/B6 and R16F2n/R2. RFLP analyses performed with Tru1I and HhaI enzymes, allowed the identification, only in the symptomatic plants, of phytoplasmas belonging to subgroup 16SrI-B (‘Candidatus phytoplasma asteris’). The detection and identification of aster yellows phytoplasmas in E. linifolium in Italy represents the first report in this species worldwide. Phytoplasmas belonging to 16SrII group (‘Ca. P. aurantifolia’) were detected in 2010 in E. cheiri (sin. C. cheiri), a different species cultivated in south-eastern Iran, showing witches’ broom and phyllody. Considering that E. linifolium is propagated by seed, it is very likely that leafhoppers are involved in 16SrI-B phytoplasma spreading in this species.