FIRST REPORT OF A ‘CANDIDATUS PHYTOPLASMA ZIZIPHI’ RELATED STRAIN ASSOCIATED WITH PEACH DECLINE DISEASE IN INDIA
J.A. Khan, J. Kumar, P.D. Thakur, A. Handa, K. Jarial
In mid 1980s, peach (Prunus persica) trees growing in Himachal Pradesh (India) showed phytoplasma-like symp- toms consisting of yellowing, marginal rolling and scorching of the leaves that conferred a burnt-like appearance to the trees. Fruits shrivelled and dropped prematurely and affect- ed plants declined and died. Although the association of a phytoplasma with this disease had already been established (Thakur et al., 1998), the species of the putative agent had re- mained unidentified. Total DNA isolated from nine diseased peach trees was subjected to nested PCR employing univer- sal primers P1/P7 followed by P1/Tint primers, and yielded fragments of 1.6 kb. PCR products from five diseased trees were digested with AluI, BfaI, DraI and EcoRI. The RFLP profile for each enzyme was identical, indicating that all trees contained a similar phytoplasma. PCR amplicons from three trees were cloned and sequenced. 16S rDNA sequences from all clones were identical and the consensus sequence, archived in GenBank under accession No. JQ695914 was shown by BLAST analysis to be nearly identical (99%) to that of ‘Candidatus Phytoplasma ziziphi’ (16SrV-B). A dendrogram drawn using 16S rDNA sequences was in line with BLAST comparisons and confirmed that the peach decline phyto- plasma is related to members of the 16SrV-B subgroup. A virtual RFLP pattern employing 14 restriction enzymes also showed its relatedness to 16SrV-B subgroup members (Wei et al., 2007). On the basis of sequence identity, phylogenetic analysis and virtual RFLP of 16S rDNA, the phytoplasma associated with peach decline disease in Himachal Pradesh can be identified as a strain of ‘Ca. P. ziziphi’. This is the first definitive identification of a 16SrV-B subgroup phytoplasma associated with peach decline disease in India.