Cherry Lethal Yellows and Decline Phytoplasmas

Cherry is an important fruit crop for which severe decline symptoms associated with the presence of phytoplasmas has been reported in the past years. A cherry decline, termed “leptonecrosis,” was first reported in Emilia region of northern Italy in the early 1930s. An outbreak of a lethal yellows disease on Chinese cherry in the Sichuan province of China in 1989 caused severe losses to the local cherry industry. Electron microscopy study of diseased tissues and disease remission resulting from tetracycline treatment of infected plants suggested that the cherry lethal yellows (CLY) disease may be caused by a phytoplasma . Based on the phylogenetic analysis of the 16S rRNA gene, RFLP analysis of ribosomal protein gene sequences and Southern hybridization analysis of total genomic DNA using selected DNA probes derived from the Elm Yellows (EY) phytoplasma (group 16SrV, subgroup 16SrV-A), it was proposed that the CLY phytoplasma belongs to the elm yellows phytoplasma group (16SrV), and represents a new subgroup, 16SrV-B, distinct from other members of 16S rRNA group V or 16SrV. A recent study showed the presence of 16SrV-B phytoplasmas in severely declining cherry trees in northern Italy. More recently phytoplasmas belonging to two ribosomal groups (stolbur, 16SrXII-A and clover yellow edge, 16SrIII-B, respectively) were identified in cherry plants showing a quick dieback before the harvesting season, this disease is named decline. The symptoms associated with the diverse phytoplasmas in Italy do not differs from each other and are quite similar to the CLY described in China.