Biological and molecular characterization of the phytoplasma associated with tomato big bud disease in Zanjan province, Iran

Tomato big bud (TBB) is an economically important disease of tomato (Lycopersicon esculentum Mill.) in various regions of the world. In 2013 surveys of Zanjan province (Iran) tomato fields, symptoms of TBB disease were observed. The disease agent was successfully transmitted by grafting from a naturally symptomatic tomato in Zanjan to tomato and eggplant and from tomato to periwinkle via dodder (Cuscuta campestris Yank.) transmission. In inoculated plants phytoplasma-type symptoms were produced. Expected length DNA fragments of nearly 1,800 and 1,250 bp were respectively amplified from naturally infected tomato and experimentally inoculated plants in direct polymerase chain reaction (PCR) using phytoplasma primer pair P1/P7 or nested PCR using the same primer pair followed by R16F2n/R16R2 primers. Virtual restriction fragment length polymorphism (RFLP) of nested PCR products (1.2 kbp) showed that Zanjan TBB (ZTBB) phytoplasma is related to subgroup A in 16SrVI (clover proliferation) phytoplasma group. Phylogenetic analysis of full length 16S rDNA classified ZTBB with 16SrVI-A subgroup. This is the first report of biological and molecular characterization of a phytoplasma associated with TBB disease in Zanjan province.