Date-Pathogen Pipeline: A Pipeline to Detect Pathogenic DNA in Date Palm Cultivars
Authors: Thareja Gaurav , Mathew Sweety , Mathew Lisa Sara , Ali Mohamoud Yasmin , Suhre Karsten , Malek Joel A 
Published: July 2019

Viruses, Bacteria and Fungal pathogens have been responsible for destruction and degradation of plants worldwide. Most often, these pathogens live a symbiotic relationship with the plant, enhancing plant growth and at times as predators, causing a wide variety of diseases. Date palms are cultivated widely in the Middle Eastern region due to their multi-faceted uses and are valued most for their nutritious fruit – the date. The trees flourish in deep sandy loam soils and can also grow in salty and alkaline soils. An old Arab folk saying “Its feet in water and its head in file” aptly describe Date Palm trees. Therefore, the importance of Date Palm trees to Qatar and in broad to the region (Arabian Peninsula) cannot be undermined.

Date palm cultivation is hindered by several constraints; especially it's vulnerability to a wide range of bacterial, viral and fungi pathogens present in the environment. Outbreaks of diseases like Bayoud disease caused by Fusarium oxysporum was reported in Morocco and spread to neighboring countries Algeria and Tunisia, resulting in destruction of millions of trees since its outbreak a century ago. This outbreak impacted socio economic conditions of farmers as poor quality but disease resistant cultivars started dominating the landscape at the expense of commercial cultivars. In Qatar, localized incidences of disease in Date Palm trees have been reported. In 2003, Department of Agricultural Development reported a first instance of Neck bending disease on Date Palm trees growing alongside the road of Majlis AL-Taawin located in Doha, Qatar. Neck Bending was previously reported in Iraq. Therefore, continuous efforts are needed to scan for opportunistic environmental pathogens, which in future can lead to disease outbreaks. In this work, we present our findings of environmental pathogens detected with our new Date-Pathogen pipeline (DPP) using geographical sampling of Date Palm Trees covering all municipalities in the State of Qatar.

A total of 96 leaf samples were sequenced on HiSeq2500 using libraries prepared by Genotyping-by-Sequencing methodology. We identified 4 different variants of the virus Enterobacteria spp in 31 samples. They belonged to two municipalities, Al Wakrah and Al Rayyan region. We uncovered two different bacteria namely Propionibacterium acnes and Staphylococcus epidermidis in a total of 52 samples growing in the Al Rayyan Municipality region in Qatar. Eight different variants of Propionibacterium was found in all the samples except one. The above bacterial pathogens are causative agents to cause acnes in human skin and known to have no effects on plants. A recent study in 2014 has reported an example of inter kingdom bacterial host transfer involving human pathogen Propionibacterium acnes Zappae and grapevine plants. This could suggest that the strain of Propionobacterium acnes identified in our samples might be in future case of interkingdom transfer from human to date palm trees. Two fungal pathogens – Saccharomyces cerevisiae and Fusarium graminearium were also found in 42 samples. It has been shown that Saccharomyces cerevisiae produces plant hormone indole-3-acetic acid (IAA), which in sufficient quantity triggers fungal cells to be more infectious in host organism. This infection was found in trees from Al Wakrah and Al Raayan municipalities. Fusarium graminearium are known to cause fusarium head blight in wheat, barley and oat. Previously, other Fusarium species oxysporum have been found to cause Bayoud disease in date palm trees which have resulted in degradation of date palm trees in Morocco and Algeria. However, Fusarium graminearium is reported in Qatar for the first time in date palm trees growing at Doha, Al Khor, Al Daayen, Al Shamal and Umm Salal municipalities. The above results are preliminary analysis and will be explored further in the next few months.