Molecular identification and pathogenicity of Phytophthora nicotianae-caused bud rot disease of Washingtonia palms in Saudi Arabia and use of Lysobacter enzymogenes as a bioagent in an in vitro study

Mohamed A El Meleigi,Khaled A Al Jamhan,Ahmad A Al Rokibah,Ayman F Omar,Noha A Sukar,Abdullah Alsohim

doi:10.1186/s41938-019-0107-y

Mohamed A El Meleigi, Khaled A Al Jamhan + Show 4 more

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https://doi.org/10.1186/s41938-019-0107-y

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Abstract

Severe terminal bud rot disease symptoms of Washingtonia, Washingtonia robusta, palms were observed in the 5-year-old trees in a farm located at the north of Al Shehia governorate, Qassim region, Saudi Arabia. The fungus found associated with the diseased palm buds was isolated in the laboratory, and pathogenicity tests were conducted on healthy 1-year-old Washingtonia palms, at an experimental station, Agriculture and Veterinary Medicine. Pathogenicity tests showed that a single fungus caused typical symptoms of bud rot on the inoculated trees. Petiole bases and terminal buds were rotted after 5–6 weeks of inoculation. The pathogen was identified through microscopy and characterized molecularly, using internal transcribed spacer (ITS) regions of ribosomal DNA, as a fungal-like organism Phytophthora nicotianae (synonym = P. parasitica). Experiments were conducted on the biological control of the pathogen in the laboratory, and a promising RN13 isolate of Lysobacter enzymogenes was selected for further study. This study seems to be the first report of bud rot disease of Washingtonian palms caused by P. nicotianae in Saudi Arabia. Great attention should be given to this disease because it is soil borne and may be transmitted to the date palm crop.

Highlights

Mexican Washingtonian trees, Washingtonia robusta, are a member of the family Arecaceae, which is native to Northwestern Mexico
Several Lysobacter spp. including L. enzymogenes, L. antibioticus, and L. capsici (Hayward et al 2010) reported to have the potential as one of the biological control agents for plant diseases. 3.1T8 and OH11 strains of L. enzymogenes were very effective in inhibiting the mycelial growth of Phytophthora capsici, Pythium ultimum, Py. aphanidermatum, Rhizoctonia solani, Fusarium graminearum, Ralstonia solanacearum, and Sclerotinia sclerotiorum (Christensen & Cook, 1978, Folman et al 2003, Jiang et al 2005, and Qian et al 2009)
The objective of this research was to survey the bud rot disease of Washingtonia palms caused by P. nicotianae and the isolation and identification by molecular methods based on sequencing of internal transcribed spacer (ITS) regions and to suggest a method for disease control

Summary

Introduction

Mexican Washingtonian trees, Washingtonia robusta, are a member of the family Arecaceae, which is native to Northwestern Mexico. It is one of the most regularly planted palm trees around the world as an ornamental plant (Broschat 2018). Phytophthora nicotianae (synonym = P. parasitica) has been reported to infect ornamental palms, more than 301 different ornamental plants and vegetable hosts such as onion, Allium cepa; carnation, Dianthus caryophillus; tomato, Lycopersicum esculentum; and poinsettia, uphorbia pulcherrima. Several Lysobacter spp. including L. enzymogenes, L. antibioticus, and L. capsici (Hayward et al 2010) reported to have the potential as one of the biological control agents for plant diseases. Several Lysobacter spp. including L. enzymogenes, L. antibioticus, and L. capsici (Hayward et al 2010) reported to have the potential as one of the biological control agents for plant diseases. 3.1T8 and OH11 strains of L. enzymogenes were very effective in inhibiting the mycelial growth of Phytophthora capsici, Pythium ultimum, Py. aphanidermatum, Rhizoctonia solani, Fusarium graminearum, Ralstonia solanacearum, and Sclerotinia sclerotiorum (Christensen & Cook, 1978, Folman et al 2003, Jiang et al 2005, and Qian et al 2009)

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