[en] Four predominant isolated pathogens have been identified during survey of rice diseases in three regions in Madagascar. These pathogens were the bacteria Xanthomonas oryzae pv. oryzae and Pseudomonas fuscovaginae and the fungi Alternaria sp. and Curvularia lunata. These pathogens are causing significant yield reduction on rice, which is the staple food in this country. After the identification of those pathogens, the objective of this work was to identify appropriate control measures against them.
Plants extracts has been traditionally used to control diseases in other plant species. Nowadays, the problem of residues of phytopharmaceutical product, reinforce the need for research on the development of natural plant extracts to control plant diseases. Madagascar has many endemic plant of interest and we have evaluated the antimicrobial properties of essential oils from Malagasy plants.
The main object of this study is the in-vitro screening of essential oils to control the pathogens isolated on rice in Madagascar. Thirty nine essentials oils from Madagascar had been tested.
Activity of essentials oils on Pseudomonas fuscovaginae, Alternaria sp. and Curvularia lunata had been tested using broth media and on agar medium for Xanthomonas oryzae pv. oryzae. The growth of the pathogen (bacteria and conidia) in the presence of the essential oil was evaluated and compared to a control. Nine of the 39 essentials oils showed interesting antimicrobial activity with an efficiency more than 70% against at least one bacterial pathogen. One essential oil inhibited the growth of the two pathogens tested. For fungal pathogens, three essential oils presented an efficiency of more than 70% against at least one fungal pathogen.
These results confirm that some essential oils present an interesting antimicrobial activity. The in-situ confirmation on plant of this activity is currently ongoing.
