Identification of phytoplasma strains associated with witches’ broom and yellowing in Ziziphus jujube nurseries in Iran

Abstract

Phytoplasma symptoms, including proliferation, witches’ broom, leaf rolling and yellowing, were observed in jujube (Ziziphus jujube) nurseries in the East of Iran. Total nucleic acid was extracted from symptomatic and symptomless plants, and was tested for phytoplasma presence using nested PCR. Amplicons of about 1.8 kb (primer pair P1/P7) and 1.25 kb (R16F2n/R16R2) were obtained from all symptomatic plants but not from symptomless plants. Restriction fragment length polymorphism (RFLP) analysis of R16F2n/R2 amplicons using KpnI, HaeIII, RsaI, AluI, HpaII, HhaI, TaqI, MseI, BfaI and ThaI restriction enzymes showed two RFLP patterns referable to 16SrI and 16SrVI phytoplasma groups. The consensus sequences of Z. jujube yellowing and witches’ broom of six samples correspond to ‘Candidatus Phytoplasma asteris’ and ‘Candidatus Phytoplasma trifolii’-related strains. Two R16F2n/R16R2 16S rDNA sequences representative of each RFLP profile, one each from witches’ broom (accession number MK379605) and yellowing (MK379604) host symptoms, were submitted to the GenBank. Phylogenetic analysis confirmed that the phytoplasma strains associated with jujube yellowing clustered within the 16SrI phytoplasma clade, and those associated with witches’ broom clustered within the 16SrVI clade. Restriction analysis confirmed that virtual RFLP patterns of the jujube yellowing and witches’ broom phytoplasma strains were identical to the reference pattern of 16SrI-B and 16SrVI-A. This is the first report of these phytoplasma strains associations with witches’ broom and yellowing in jujube plants.