Abstract
Citrus blast and black pit that became increasingly important bacterial diseases are caused by Pseudomonas syringae pv. syringae. This study aimed to evaluate the antibacterial potential of Bacillus species strains and garlic extracts against two P. syringae isolates (BAT13 and DAPP-PG115). The Bacillus species strains were isolated from symptomless citrus leaves. Under in vitro conditions, 21 Bacillus species strains and garlic extract displayed antibacterial activity against the pathogen. Under greenhouse conditions, antagonistic bacteria, garlic extract, and copper sulfate confirmed their antimicrobial effect on P. syringae and reduced significantly the extend of stem necrosis 10 weeks after inoculation by BAT13 up to 60.55, 56.11, and 45.83%, and by DAPP-PG115 up to 70.83, 62.5, and 46.52%, in respect to relevant treatments. Garlic extract was the most effective treatment in our hands, and it suggests that Allium sativum extract could be used to control and prevent infection by the pathogen.
Highlights
Citriculture represents a strategic sector in Tunisia that covers around 24,000 ha with c. 6.4 million trees
Among the bacterial diseases that pose a threat to citrus and reduce the yield are the citrus blast and black pit, caused by Pseudomonas syringae pv. syringae (Snowdon 1990)
Identification of the antagonistic bacteria Antagonistic bacteria which exhibited in vitro antibacterial activity against P. syringae pv. syringae were biochemically identified
Summary
Citriculture represents a strategic sector in Tunisia that covers around 24,000 ha with c. 6.4 million trees. Citriculture represents a strategic sector in Tunisia that covers around 24,000 ha with c. Annual production is estimated around 300,000 tons of fruit (DGPA 2016). Among the bacterial diseases that pose a threat to citrus and reduce the yield are the citrus blast and black pit, caused by Pseudomonas syringae pv. Beiki et al (2016) reported new citrus pathogenic strains of Pseudomonas orientalis, P. simiae, P. lurida, P. moraviensis, and P. monteilii. Blast results in expanding lesions on citrus leaves and stems leading to defoliation of trees in severe attacks. Black pit results in dark-colored, sunken blemishes on fruits on lime and lemon (Fawcett et al 1923). Syringae causing citrus blast and black pit was first reported by Boubaker (1986) on sour orange, Citrus aurantium, by Abdellatif In Tunisia, P. syringae pv. syringae causing citrus blast and black pit was first reported by Boubaker (1986) on sour orange, Citrus aurantium, by Abdellatif
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