First report of ‘Candidatus Phytopalsma asteris’ subgroup 16SrI-Bassociation with a witches’ broom disease of fennel

Abstract

Fennel is an economically important spice crop grown in many countries worldwide. In April 2016 witches’ broom symptoms were observed in fennel plants at fields of IARI, New Delhi, India. The symptomatic samples were analysed for phytoplasma DNA presence by PCR using the phytoplasma universal primer pair P1/P7 and nested PCR assay using primers R16F2n/R16R2. Amplicons of the expected sizes (1, 800 and 1, 250 bp respectively) were amplified in all the symptom-bearing fennel plants, but not from the symptomless plants used as negative controls. A nested PCR product was directly sequenced and deposited in GenBank. The BLASTn search analysis using the 16S rDNA sequenced fragment showed that the phytoplasma associated with fennel witches’ broom had 99% nucleotide identity with the sequences of ‘Candidatus Phytoplasma asteris’-related strains. The phylogeny and virtual RFLP analysis revealed that the phytoplasma belonged to the 16SrI-B subgroup. To our knowledge, this is the first report of infection of fennel by a strain of 16SrI-B phytoplasmas.