In vitro antifungal activity of endophytic bacteria isolated from date palm (Phoenix doctylifera L.) against fungal pathogens causing leaf spot of date palm

H H Al-Nadabi,S N Maharachchikumbura,A A Al-Nabhani,A M Al-Sadi,R Velazhahan,N S Al-Buraiki

doi:10.1186/s41938-021-00413-6

H H Al-Nadabi, S N Maharachchikumbura + Show 4 more

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https://doi.org/10.1186/s41938-021-00413-6

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Abstract

BackgroundDate palm ((Phoenix doctylifera L.) suffers from several fungal diseases. The endophytic microorganisms present in higher plants generally offer protection to their host plants against invading phytopathogenic fungi and bacteria. In the present study, endophytic bacteria associated with date palm leaves were isolated and their in vitro antagonistic potential against fungal pathogens causing leaf spots in date palm was demonstrated.ResultsEndophytic bacteria were isolated from date palm leaves of 3 different cultivars viz., Nighal, Khalas and Khinaizi and evaluated for their inhibitory activity against leaf spot pathogens of date palm viz., Fusarium solani, Alternaria sp., Nigrospora sp., Thieloviopsis sp., Curvularia subpapendrofii and Tilletiopsis minor using an in vitro dual culture assay. Of the 24 endophytic bacterial strains tested, the endophytes designated B1, B7, B8 and B9 obtained from cv. Nighal showed inhibitory activities (more than 55% mycelial growth inhibition) against F. solani and Alternaria sp. None of the bacterial endophytes inhibited the growth of other fungal pathogens tested. These antagonistic bacterial strains were identified as Pantoea septica on the basis of 16S rRNA gene sequence analysis. The hyphae of F. solani and Alternaria sp. exhibited morphological abnormalities such as shrinkage and disintegration when grown in the presence of antagonistic bacterial endophytes. The cell-free culture filtrates of the bacterial endophytes caused inhibition of mycelial growth and induced leakage of electrolytes from the mycelia of F. solani and Alternaria sp. This is the first study that describes inhibition of the date palm pathogens F. solani and Alternaria sp. by P. septica.ConclusionEndophytic Pantoea septica strains isolated from date palm leaves inhibited the mycelial growth of F. solani and Alternaria sp. and induced morphological changes in their mycelia. The culture filtrates of these bacterial strains also inhibited the mycelial growth and caused leakage of electrolytes from the mycelia of F. solani and Alternaria sp. These promising bacterial strains can be exploited as biocontrol agents to control F. solani and Alternaria sp.-induced leaf spot diseases of date palm.

Highlights

Date palm ((Phoenix doctylifera L.) suffers from several fungal diseases
Isolation and in vitro screening of endophytic bacteria Twenty-four endophytic bacterial strains (B1–B24), with distinguished colony morphologies, were isolated from the leaves of date palm collected from Nighal (B1–B13), Khinaizi (B14–B19) and Khalas (B20–B24) cultivars
The antagonistic activities of the bacterial strains were tested against F. solani, Alternaria sp., Nigrospora sp., Thieloviopsis sp., C. subpapendrofii, T. minor and Tilletiopsis sp. in vitro by using a dual culture technique

Summary

Introduction

Date palm ((Phoenix doctylifera L.) suffers from several fungal diseases. Endophytic bacteria associated with date palm leaves were isolated and their in vitro antagonistic potential against fungal pathogens causing leaf spots in date palm was demonstrated. Many fungi are reported and proven to cause leaf spot diseases in date palms such as: Alternaria, Mycosphaerella, Chaetosphaeropsis, Phoma and Phomopsis (El-Deeb et al 2007). In Oman, Alternaria alternata, A. burnsii, A. arborescens, A. jacinthicola, A. tomato and A. slovaca are the major fungal pathogens of leaf spot disease of date palm (Al-Nadabi et al 2018). Despite these challenges, date palms withstand and show adaptations features

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