FIRST REPORT OF A 16SrIX GROUP (PIGEON PEA WITCHES'-BROOM) PHYTOPLASMA ASSOCIATED WITH GRAPEVINE YELLOWS IN IRAN

Abstract

Association of 16SrXII-A phytoplasmas with grapevine yellows (GY) has been previously reported from Fars and Lorestan provinces of Iran (Salehi et al., 2014). During 2013-2014 surveys, symptoms resembling those of GY disease including thickening and downward rolling of leaves, vein chlorosis and necrosis, shoot dieback and stunting were observed in vineyards of Shiraz area (Fars province, Iran). Total DNA samples extracted from eight symptomatic and eight symptomless vines were tested for phytoplasma presence. In direct PCR using primers P1/P7 and nested PCR using primer pairs P1/P7 followed by R216F2n/R16R2 (Lee et al., 1998), respectively amplicons of ca. 1.8 and 1.2 kb were amplified from symptomatic but not from symptomless vines. Samples that yielded P1/P7 amplicons (4/8) were cloned and sequenced; obtained sequences showed 100% identity. A BLAST search using full length 16S rRNA gene sequence of a representative of these sequences (GenBank Accession No. KX011516) revealed that the sequence shared 99% homology with Indian Brassica rapa phyllody phytoplasma (HM988986), a representative of 16SrIX-C subgroup. Computer-simulated restriction analysis using iPhyClassifier showed that the RFLP profile of the Shiraz GY (SGY) phytoplasma 16S rDNA sequence was identical (similarity coefficient 1.00) to Picris echioides yellows phytoplasmas (Y16389) representative of subgroup C of the 16SrIX group. Phylogenetic analysis revealed that SGY phytoplasma clustered with16SrIX group phytoplasmas closer to Indian B. rapa phyllody phytoplasma, a 16SrIX-C member. To our knowledge, this is the first report of natural infection of grapevine by a 16SrIX phtoplasma in Iran.