Pathogenicity, host range and phylogenetic position of Agrobacterium species associated with sugar beet crown gall outbreaks in Southern Iran
2017
Mafakheri, Hamzeh | Taghavi, S Mohsen | Banihashemi, Zia | Osdaghi, Ebrahim | Lamichhane, Jay Ram
In autumn 2013, an alert concerning a suspected outbreak of sugar beet disease under field conditions has received from Eghlid county, Fars province, Southern Iran. Field surveys were performed following the alert and plants affected with crown gall and tuber deformation were observed. Diseased plants were randomly collected and brought to the laboratory for the isolation and characterization of the causal agent through biochemical, pathogenicity and host range tests under greenhouse conditions on seven crop, ornamental and weed species including carrot, sunflower, and tomato, Christmas kalanchoe and rose ornamentals, and rough milk thistle weed, in addition to sugar beet. Further, sugar content of both infected and non-infected plants was determined. Based on biochemical and molecular tests, the causal agents were identified as members of the Agrobacterium tumefaciens species complex. In pathogenicity and host range tests, all bacterial strains induced lateral and globular galls on the plant species tested. Phylogenetic analysis using the sequences of gyrB housekeeping gene revealed that A. tumefaciens strains isolated from sugar beet belonged to the biovar 1 species complex but divided into two different genomo-species (G3 and G7). No phylogenetic similarities were found among the A. tumefaciens species complex strains isolated from fig, peach, rose, and sugar beet in Iran. The sugar content analysis showed 3 % reduction in sugar content of the infected tubers compared to the healthy ones, which resulted in 24 % reduction in the tubers’ price. Our study reports the outbreaks of an economically important disease, which may further spread and affect the sugar beet industry in Southern Iran.
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