Identification of two phytoplasma groups in Alwijam-affected date palms and their possible alternative hosts in Saudi Arabia

Date palm is affected by the Alwijam disease in many regions of the Kingdom of Saudi Arabia. 
The Alwijam phytoplasma survey was conducted in new date palm-growing areas of Saudi Arabia. 
Leaf samples were collected from 943 date palm plants, with and without Alwijam symptoms. The 
DNA was extracted from leaf midribs and indexed by a nested PCR reaction using different sets of 
16S rRNA phytoplasma generic primers P1/P7 or R16mF2/R16mR1 and R16F2n/R16R2. PCR 
amplicons were cloned and sequenced. The consensus sequences from the Alwijam phytoplasma 
were submitted to GenBank and compared with those from other phytoplasma. Two phytoplasma 
groups were identified; 16SrI (Candidatus Phytoplasmas asteris) in Alhasa, and 16SrII 
(aurantifolia) in other locations of Saudi Arabia. Ocimum basilicum and Medicago sativa were 
found as possible alternative hosts for Alwijam 16SrII phytoplasma.