Substances Secreted by Endophytic Bacterium as a Treatment Against Phloem Inhabiting Phytopathogens

Yellow diseases caused by phloem inhabiting phytopathogens is common in different plant species. In carrot, the pathogen is Ca. Liberibacter solanacearum (Lso), while in periwinkle and in grapevine the pathogen is Ca. Phytoplasma. Yellows disease of carrots is a widespread and destructive disease causing a wide range of symptoms such as deformation of edible root and atypical growth of leaves in the form of "witch’s broom". This disease may cause total yield loss. In a previous study, we isolated a beneficial endophyte - DLB (Dyella-like bacterium) that have shown to reduce symptoms of grapevine yellows caused by Ca. Phytoplasma.

The aim of this study was to examine whether substances, secreted by DLB, can inhibit the development of Ca. Phytoplasma and Lso infection in periwinkle and carrot, respectively.

The substances secreted by DLB were identified by HPLC and GC-MS. Synthetic compounds, analogues to those identified by the biochemical analysis, were applied on yellows infected carrots and periwinkles. The compounds effect on the titer of Ca. Phytoplasma and Lso was examined by qPCR.

Spraying the synthetic compounds on yellows infected carrots caused a significant reduction in the titer of Lso in comparison to untreated infected plants. However, phytoplasma levels in periwinkle were not affected by the same treatment. Further research is required to examine the potential of these compounds as a treatment against yellows disease of carrot, as well as other phloem-restricted phytopathogens