Control of Agrobacterium tumefaciens with Essential Oils Compared to Antagonistic Agrobacterium radiobacter Strain K84

Abd-El-Aziz, Rabab M.; Abd El-Rahman, Ashraf F.; Hendi, Dina M.G.

doi:10.21608/ejp.2021.107286.1047

Control of Agrobacterium tumefaciens with Essential Oils Compared to Antagonistic Agrobacterium radiobacter Strain K84

Document Type : Original Article

Authors

¹ Plant Pathology Research Institute, Agricultural Research Center, 12619, Giza, Egypt

² Horticulture Research Institute, Agricultural Research Center, 12619, Giza, Egypt

10.21608/ejp.2021.107286.1047

Abstract

Crown gall is one of the most hazardous diseases for nurseries of stone fruit plants. Biological control of crown gall caused byAgrobacterium tumefaciens using Agrobacterium radiobacter K84 is more comparatively effective in disease control compared to chemical means. In the present work, the distinguished components of essential oils of caraway (Carum carvi L.) were carvone (79.38157%) and limonene (18.78265%), and those for thyme (Thymus vulgaris L.) were identified as thymol (14.79336%), 1,8-Cineol (14.45795%), borneol (13.22024%), β-caryophyllene (10.86938%) and bornyl acetate (5.08278%). The inhibition zone produced by the antagonist A. radiobacter against A. tumefaciens 27AS_ Pp4 was 11.8 mm in diameter, whereas it was 10.2 and 11.0 mm in caraway and thyme essential oils, respectively. The minimal inhibitory concentration (MIC) of essential oils against A. tumefaciens 27AS_Pp4 was 12.8 μl/ml of both caraway and thyme as compared with the minimal bactericidal concentration (MBC) being 25.6 and 12.8 μl/ml for caraway and thyme, respectively. When A. tumefaciens 27AS Pp4 was treated with caraway and thyme, the crystal violet uptake was increased. No disease syndromes were observed on apricot (Prunus armeniaca L.) seedlings inoculated with the pathogen A. tumefaciens 27AS_Pp4 and the antagonist A. radiobacter. Moreover, a significant decrease in the number of galls was observed in caraway and thyme essential oil treatments compared to the positive control. The fresh and dry weight of galls per plant confirmed the effectiveness of caraway and thyme treatments. The treatment of caraway essential oil showed a significant decrease in the fresh weight of shoots and roots compared to both positive and negative controls and A. radiobacter treatments. No significant differences in the fresh weight of shoots and roots in thyme oil treatment compared to negative control and A. radiobacter. Determination of the dry weight of shoots and roots comparatively confirmed these results. On the other hand, the essential oil of caraway showed a significant decrease in plant length compared to thyme, A. radiobacter, and positive and negative control treatments. In the case of thyme oil, the length of the plant has increased significantly compared to the negative control, with no significant difference between thyme oil and A. radiobacter treatments. These results suggest that the essential oils of caraway and thyme have a reasonable potential for controlling crown gall disease. Consideration should be given to the potential effect of the essential oil of caraway on plant growth. Further work with different horticulture seedling nurseries is needed.

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