Detection and identification of phytoplasmas associated with longan witches' broom in Vietnam

Longan (Dimocarpus longan Lour.) belongs to the family Sapindaceae and is an important fruit tree grown mostly in the Southern part of Vietnam. In January 2010, plants of longan Tieudabo variety showing witches’ broom symptoms were observed at orchards in Dong Nai province, Southeast region. Nested PCR assays with universal phytoplasma primers amplifying 16S rRNA on nucleic acid extracted from symptomatic longan samples allow detecting expected length amplicons. RFLP analyses revealed similarity to the reference strains elm yellows (group 16SrV) and stolbur (group 16SrXII). The presence of a mixture of phytoplasmas was confirmed by nested PCR assays with group-specific primer pairs R16(I)F1/R1 and R16(V)F1/R1 together with sequencing of amplicons. To our knowledge, this is the first report of multiple phytoplasma infection associated with witches’ broom disease in longan in Vietnam.