Background Date 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. Results Endophytic 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. Conclusion Endophytic 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.
This paper reports the occurrence of a leaf blotch disease in Ficus religiosa in Sri Lanka. The disease first appears as small, irregular, yellow specks in leaves at later stages of maturity and with time the infected areas become necrotic and gradually enlarge. At advanced stages the whole leaf turns yellow with brown blotches and is shed. The causal agent was identified as Botryosphaeria sp. The necrotic blotches are associated with erumpent fruiting bodies of the fungus, ascomata. Ascomata are solitary or botryose and are found on both sides of leaves. Asci are with numerous pseudoparaphyses and ascospores were observed. Colony developed on water agar medium showed hyaline, aseptate conidia and mature brown conidia. In the presence of leaf blight caused by Glomerella cingulata, the leaf blotch symptoms appeared much later, about 10-12 weeks after the new flush. The diseased leaves do not last long as F. religiosa, being a deciduous species, sheds leaves seasonally. However, the fallen leaves, unless eliminated, may provide a good source of inoculum for infection of the new flush. Commercial fungicide, BULLET 50, inhibited the in vitro growth of Botryosphaeria sp. This is the first report on a blotch disease attacking leaves of F. religiosa in Sri Lanka.
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