Molecular detection and characterization of a 16SrII-D phytoplasma associated with streak yellows of date palm in Oman

Abstract

Date palm is the most important fruit crop in Oman, covering about 50% of the agricultural area in the country. During a survey in 2018–2020, symptoms resembling phytoplasma diseases were observed in date palms in Muscat, Oman. Date palms showed streak yellows and dryness of young and mature leaflets and leaves. Polymerase chain reaction (PCR) assays were conducted using the universal primer pairs P1/P7 followed by R16F2n/R16r2n. In addition, the phytoplasma genes imp, secA, and tuf were also targeted in semi-nested PCR assays by using specific primers for each gene. Symptomatic trees were positive for phytoplasma presence in nested and semi-direct PCR, however, no amplification was observed from the symptomless and negative control. Sequence analysis of the rRNA, imp, secA, and tuf genes confirmed that the phytoplasma associated with streak yellow date palm (SYDP) is a strain of the 16SrII-D subgroup. This is the first record of association of a phytoplasmas of the 16SrII-D subgroup with date palms in Oman. This finding increased our knowledge about the distribution of phytoplasma diseases in date palms in the world.