Austroagallia sinuata transmission of “Candidatus Phytoplasma aurantifolia” to Zinnia elegans
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KeywordsVector tranmission 16SrII-B Ornamental plant disease Phytoplasma
Phytoplasmas are insect-vectored pathogens causing characteristic and destructive diseases in ornamental plants. Although Zinnia elegans phyllody (ZeP) was reported from Iran in 2017, no insect vector was identified (Hemmati and Nikooei 2017). Here we report successful transmission of ZeP phytoplasma to Z. elegans by Austroagallia sinuata. For transmission assays, a total of 20 Z. elegans seeds were provided and sown in 20 pots under cages. A total of 78 (5–7 individuals per cage) adults of A. sinuata collected from naturally-infected Z. elegans in municipal lands and parks in Bandar Abbas were transferred to 15 of the pots (at four leaf stage) for 2 weeks as inoculation access phase. Five cages with five healthy Z. elegans plants were not exposed to leafhoppers. The plants in each cage were continuously monitored for symptom expression up to 60–80 days post inoculation. The naturally infected Z. elegans, insects and the symptomatic Z. elegans plants in experimental cages after transmission test were analyzed for the presence of phytoplasma using PCR assays with primer pair P1/P7 followed by R16f2n/R16r2 (Gundersen and Lee 1996). Eight to 10 weeks after inoculation, 13 of 15 inoculated plants showed typical symptoms, including bud proliferation, phyllody, virescence, general chlorosis, and stunting. Nine amplified R16f2n/R16r2 primers PCR products from three experimentally vector challenged Z. elegans, three naturally infected Z. elegans and three insects were sequenced bidirectionally and one sequence from each host was deposited in GenBank (Accession Nos. MK424862-4). All sequences were aligned (Clustal Omega) and they shared 100% identity to each other, and BLAST analysis of the 16S rDNA sequences revealed that the phytoplasmas were all strains of 16SrII subgroup D. In addition, phytoplasma sequences yielded the same RFLP patterns after restriction with AluI, HhaI, HinfI, HpaII, MseI, RsaI, Sau3AI and TaqI enzymes. To our knowledge, this is the first evidence of phytoplasma vector ability of A. sinuata in the world.
- Gundersen DE, Lee IM (1996) Ultrasensitive detection of phytoplasma by nested-PCR assays using two universal primer sets. Phytopathol Mediterr 35:144–151 http://www.jstor.org/stable/42685262