Performance of three endophytic actinomycetes in relation to plant growth promotion and biological control of <Emphasis Type="Italic">Pythium aphanidermatum</Emphasis>, a pathogen of cucumber under commercial field production conditions in the United Arab Emirates |
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Authors: | Khaled A El-Tarabily Giles E St J Hardy Krishnapillai Sivasithamparam |
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Institution: | (1) Department of Biology, Faculty of Science, United Arab Emirates University, Al-Ain, 17551, United Arab Emirates;(2) School of Biological Sciences and Biotechnology, Faculty of Sustainability, Environmental and Life Sciences, Murdoch University, Murdoch, W.A., 6150, Australia;(3) School of Plant Biology, Faculty of Natural and Agricultural Sciences, University of Western Australia, 35 Stirling Highway, Crawley, W.A., 6009, Australia |
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Abstract: | In the current study, the performance of three endophytic actinomycetes identified as Actinoplanes campanulatus, Micromonospora chalcea and Streptomyces spiralis previously shown to reduce seedling damping-off, and root and crown rots of mature cucumber (Cucumis sativus) caused by Pythium aphanidermatum in pots under greenhouse conditions were further evaluated to determine their potential as biological control agents and
as plant growth promoters in the field under the conditions of commercial production of cucumbers in the United Arab Emirates
(UAE). When applied individually or in combination to cucumber seedlings, the three isolates significantly promoted plant
growth and yield and reduced seedling damping-off and root and crown rots of mature cucumber plants. Individually the performance
level of S. spiralis was relatively the best followed by A. campanulatus and then by M. chalcea. The three isolates (which were not inhibitory to each other) performed better, both as biological control agents as well
as plant growth promoters, when applied together than when they were inoculated individually. The ability of these three isolates
to colonize the internal tissues of roots, stems and leaves under field conditions, and to persist up to 8 weeks after seedling
inoculation, showed that they can easily adapt to an endophytic habit systemically within healthy cucumber plants. As the
three endophytic actinomycete isolates also colonized the rhizosphere and showed outstanding rhizosphere competency it is
clear that they are facultative and not obligate endophytes. The success with the three inoculants indicated that they could
well be used in place of the fungicide metalaxyl which is currently recommended for the management of Pythium diseases in the UAE. This is the first successful field use of endophytic actinomycetes as promising plant growth promoters
and biological control agents against Pythium diseases of cucumber. |
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