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

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.

The New Report of Root Rot on Fatsia japonica Caused by Phytophthora nicotianae in China

“…It preferentially infects roots and the stem basal region of the plant, although all the parts of the plant can be infected [68]. For instance, P. nicotianae was reported to cause asparagus spear and root rot in China [69], cherry stem rot and leaf necrosis in China [70], strawberry crown and leather rot in Florida [71], foot rot of citrus in Texas [72], Dianthus chinensis root rot and foliage blight in China [73], brown rot of citrus fruits in California [74], bud rot disease of Washingtonia palms in Saudi Arabia [75], Catharanthus roseus leaf blight in Bangladesh [76] and Phytophthora blight disease on konjac in Yunan [51]. Recently, it has been reported to cause root and crown rot of paulownia and sago palms in Italy [77,78].…”