Antibacterial Activity of Origanum vulgare and Rosmarinus officinalis standardized extracts Against Curtobacterium and Xanthomonas

Abstract

Diseases caused by Curtobacterium and Xantomonnas species represent an agricultural problem in crops and can generate economic impacts on the commercialization of seeds and food. Origanum vulgare L. (oregano) and Rosmarinus officinalis L. (rosemary) have rosmarinic acid and others phenolics that can lead to the control of phytopathogenic bacteria in common bean (Phaseolus vulgaris L.). This study aimed to evaluate the in vitro and in vivo antibacterial activity of O. vulgaris and R. officinalis extracts, standardized in rosmarinic acid, against Curtobacterium flaccumfaciens pv. flaccumfaciens, Xanthomonas axonopodis pv. phaseoli, Xanthomonas fuscans subsp. fuscans and Xanthomonas sp. The antibacterial effect of the extracts in bean seed was also investigated. The content of rosmarinic acid was 8.55 % for O. vulgare and 16.30 % for R. officinalis extract. It was verified the complete in vitro inhibition of the bacteria studied by both extracts at 0.8% (w/w) with exception of Xanthomonas axonopodis pv. phaseoli BRM 025302 that was completely inhibited at 1.2% (w/w)  of oregano. In addition, no symptom of phytotoxicity were noted in detached bean leaves treated with them. Under greenhouse conditions, some reduction on severity of Curtobacterium wilt by both extracts at 1% (w/w) was noted to bean cultivars BRS Sublime and BRS Estilo. Under the experimental conditions these extracts were not efficient to control the common bacterial blight caused by X. axonopodis pv. phaseoli. Both extracts are promising in the treatment of seeds, specially in related to contamination by Fusarium spp., whose percentage decreased on average an average from 94% to 10%. In addition, these bean seeds maintained the germination percentage adequate to that required by legislation. Further studies must be conducted to better investigate the potential of these standardized extracts as a bioproduct for agriculture.