Abstract
ABSTRACTDate palm phytoplasma disease (Wijam) is an emerging economical threat to the production of dates in the western provenance of Saudi Arabia. Disease symptoms were first observed in Al-Madinah region in 2014; a total of 525 healthy and symptomatic samples were collected from 34 date palm cultivars, were analysed by PCR and dot-blot hybridization. Nested PCR (nPCR) and sequencing results confirmed the presence of 16S rDNA phytoplasma, scoring 98% similarity to the 16SrI phytoplasma. Hybridization results showed that 17.4% of the collected samples were positively infected, the highest percentage of infection was found in city farms, reaching up to 13.4%. Furthermore, 16 date palm cultivars did not show any infection, while the other 18 cultivars had different percentages of infectivity. This finding may partially explain the sudden decline of date production in Al-Madinah region and suggests an alert to investigate disease control management procedures.
Highlights
Phytoplasmas are plant pathogens that belong to the Mollicutes class of prokaryotes, which are characterized by their small microscopic size and polymorphic shape due to the absence of cell-wall [1]
The Wijam disease symptoms were reported in the eastern region of Saudi Arabia in 1945 [11], Candidatus phytoplasma asteris, a member of the 16SrI group, has been identified as the causing agent of Wijam symptoms in 2002 [12,13] Reports have shown that Wijam disease resulted in a loss of more than 30–40% of date production and the death of many palm trees [14]
Representative DNA samples obtained from different locations in this study showed positive Nested PCR (nPCR) results using fU5/rU3 primers (Figure 3), confirming the presence of phytoplasma infection
Summary
Phytoplasmas are plant pathogens that belong to the Mollicutes class of prokaryotes, which are characterized by their small microscopic size and polymorphic shape due to the absence of cell-wall [1]. Date palms (Phoenix dactylifera L.)-phytoplasma is classified under the genus Candidatus, with a genome size ranging between 0.530 and 1.350 Mbp [9] and species are distinguished by its 16S rRNA gene [10]. The Wijam disease symptoms were reported in the eastern region of Saudi Arabia in 1945 [11], Candidatus phytoplasma asteris, a member of the 16SrI group, has been identified as the causing agent of Wijam symptoms in 2002 [12,13] Reports have shown that Wijam disease resulted in a loss of more than 30–40% of date production and the death of many palm trees [14]
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