Occurence of 'Candidatus Phytoplasma solani' in Association to a new host plant plum (Prunus domestica L.) in Jordan

Plum (Prunus domestica L.) is among the most important stone fruit species grown in Jordan, especially in the northern part of the country. In September 2017, orchards of P. domestica L. cv. Golden Plum, in the Mafraq region North East of Jordan, showed typical phytoplasma symptoms, such as yellowing and reddening of the leaves, stunted growth and witches’-broomed branches. Additionally, these fields also contained bindweed (Convolvulus arvensis L.) showing stunting, leaf malformation and chromatic al-teration. Leaf samples were collected from 20 symptomatic and asymptomatic plum trees and 3 symp-tomatic bindweed plants. Total genomic DNA was extracted, and samples were analyzed by PCR using the phytoplasma universal primer pairs P1/P7 followed by nested PCR with primer pair R16F2n and R16R2. DNA samples of five out of twenty P. domestica and the three bindweed samples together with the positive controls were tested positive for phytoplasma infection, yielding the expected PCR ampli-cons at 1,25 kbp. No phytoplasma was detected in symptomless Prunus trees that were sampled from the same orchard and the negative controls. Sequencing was done for each gel-purified PCR amplicon. BLASTn similarity analysis of sequences derived from the plum and the bindweed host plants revealed that the sequences of phytoplasma infecting P. domestica and C. arvensis in Jordan were highly similar (>99%) to the in NCBI GenBank® deposited Vitis vinifera L. sequences of ‘Candidatus Phytoplasma solani’ from Jordan (KC835139) and sequences from Serbia (AF248959). In silico RFLP analyses and phylogenetic analysis confirmed the affiliation of these phytoplasma strains identified in plum and bindweed in Jordan to the species ‘Ca. Phytoplasma solani’ (subgroup 16SrXII-A). Taken together, these results confirm the unique presence of ‘Ca. Phytoplasma solani’ associated to plum in the stone fruit growing area of Mafraq. The presence of the bindweed as a well-known phytoplasma reservoir and potential insect vectors may have contributed to the plum infection. To the best of our knowledge, this is the first detection of ‘Candidatus Phytoplasma solani’ infecting P. domestica so far.