Molecular identification of a 16SrII-D phytoplasma associated with sunflower phyllody in India

Abstract

Symptoms of phyllody on sunflower in India have previously been reported however, lately, the frequency of phyllody observed has increased. Transmission electron microscope (TEM) examination and PCR including nested PCR analyses using universal primers (P1/P7 and R16F2n/R2) specific to phytoplasma confirmed that the floral abnormalities are due to phytoplasma infection. Nucleotide BLAST analysis of the PCR sequences showed highest identity with sequences of phytoplasma members of the 16SrII group (‘Candidatus Phytoplasma aurantifolia’). Further, phylogenetic analysis of the 16S rRNA sequences clustered the sequences of both sunflower (HAP1) and sesame (SIP1) with other members of 16SrII. ‘Candidatus Phytoplasma’ species assignment and 16Sr group/subgroup classification using iPhyClassifier confirmed that the phytoplasma causing sunflower phyllody is a ‘Candidatus Phytoplasma aurantifolia’ related strain and belongs to the 16SrII-D group. The molecular characters of sunflower phytoplasma were compared with that of the phytoplasma associated with sesame phyllody (used as reference) which showed that the R16F2n/R2 sequences of both the phytoplasmas are identical indicating that the 16SrII-D phytoplasma that is associated with sesame phyllody can infect sunflower as well.