Molecular detection of ‘Candidatus Phytoplasma australasia’ and ‘Ca. P. cynodontis’ in Iraq

Abstract

The association of phytoplasma was investigated in symptomatic tomato (Solanum lycopersicum L.), eggplant (Solanum melongen L.), mallow (Malva spp.) and Bermuda grass (Cynodon dactylon L.) plants exhibiting witches’ broom and white leaf diseases, respectively. Total DNA was extracted from tomato (n=3), eggplant (n=2), mallow (n=2) and Bermuda grass (n=8) samples. Direct polymerase chain reaction (PCR) was performed using P1/P7 primer set, then PCR products were sequenced. Sequences obtained from tomato, eggplant and mallow shared 99% maximum nucleotide identity with phytoplasma belonging to subgroup 16SrII-D, and resulted therefore ‘Candidatus Phytoplasma australasia’-related. Sequences obtained from Bermuda grass showed 100% maximum nucleotide identity to 16SrXIV-A subgroup and were ‘Ca. P. cynodontis’-related. The study presents the first molecular confirmation and sequence data of presence of ‘Ca. P. australasia’ and ‘Ca. P. cynodontis’ in Iraq.

History and Current Status of Phytoplasma Diseases in the Middle East

“…In Israel, research on phytoplasmas started in the 1980s on grapevine, although phytoplasma symptoms have been observed in the 1970s on Bermuda grass and strawberry [ 61 ]. In Iraq, the first observation dates back to 2015, when phytoplasma that was associated with Arabic Jasmin was characterized [ 62 ]. In Lebanon, a destructive phytoplasma disease on almond was characterized in the early 2000s [ 63 ].…”

“…Tomato witches’ broom (ToWB) associated with 16SrII-D has been reported in the south of Iran. In addition, phytoplasmas belonging to the 16SrII-D subgroup have been identified in tomato grown in Oman [ 139 ], Iraq [ 62 ], Egypt [ 143 ], and Saudi Arabia [ 144 ]. Moreover, a phytoplasma of the 16SrVI group has been reported in association with this disease in Lebanon [ 145 ].…”

“…The difference could be because phytoplasmas originated from different sources or that different vectors exist in both countries [ 86 ]. In Iraq, eggplant was reported to be the host of a phytoplasma in the 16SrII-D subgroup [ 62 ].…”

“…were associated with the phytoplasma 16SrII group in Egypt and Lebanon [ 145 , 146 ]. In addition, an association between 16SrII and Arabic jasmine ( Jasminum sambac ) has been reported in Oman and Iraq [ 62 , 189 ]. In Saudi Arabia, the association between 16SrII-D and Hibiscus rosa-sinensis , Calendula officinalis , Z. Magellan , Plectranthus scutellarioides , Conocarpus lanceolatus , and Washingtonia robusta have been reported [ 190 , 191 ].…”

“…Bermuda grass ( Cynodon dactylon L.) has been reported to be infected by Bermuda grass white leaf (BGWL) disease, which is attributed to the 16SrXIV group ‘ Ca . P. cynodontis’ in Iran [ 194 ], Turkey [ 195 ], Iraq [ 62 ], and Saudi Arabia [ 196 ]. It has been confirmed that the leafhopper Exitianus capicola is the vector of this disease in Iran [ 194 ].…”