Molecular identification of 16SrII-C and 16SrII-D phytoplasma strains associated with phyllody and axillary shoot proliferation in papaya

Papaya plants exhibiting phyllody and excessive axillary shoot proliferation were observed in 10 different fields during surveys conducted in 2019 in Pune district, Maharashtra, India. The average disease incidence for phyllody and excessive shoot proliferation was 12% and 4% respectively. The presence of phytoplasma in the infected plants was confirmed by nested PCR assay using R16F2n/R2 primer pair amplifying the 16S rRNA gene and sequence analysis. In BLASTn analysis, the sequences of nested PCR products shared 99–100% identity with phytoplasmas belonging to 16SrII group. These phytoplasmas clustered with phytoplasma sequences belonging to 16SrII group in the phylogenetic analysis. The virtual restriction fragment length polymorphism pattern derived from the sequences identified these two phytoplasmas as 16SrII-C and -D. To our knowledge, this is the first report of 16SrII-C phytoplasma in papaya worldwide and 16SrII-D phytoplasma in India.