Use of Moroccan medicinal plant extracts as botanical fungicide against citrus blue mould.

The aim of this work was to find an alternative to chemical fungicides currently used in the control of postharvest citrus fruit diseases. In this study, we screened eight Moroccan medicinal and aromatic plants extracted with petroleum ether, chloroform, ethyl acetate and methanol for their anti-fungal activity against Penicillium italicum, the causal agent of citrus blue mould. The anti-fungal activity of these extracts was tested based on the disc diffusion method. Petroleum ether extracts of Inula viscosa, Asteriscus graveolens, Bubonium odorum and Thymus leptobotrys and chloroformic extract of Anvillea radiata revealed the highest significant anti-fungal activity with inhibition zones that ranged between 25·83 and 28·33 mm in diameter. In the minimal inhibitory concentration (MIC) study, we observed that petroleum ether extract of I. viscosa was the most effective extract with both the significantly largest halo (27·50 mm) and the lowest MIC (1 mg ml(-1)). The most active plant extracts in in vitro studies were tested in vivo, and results indicated that solvent extracts of the selected plant species significantly decreased the incidence and severity of blue mould, after 7 and 10 days of storage at 20°C. In addition, Halimium umbellatum methanol extract and T. leptobotrys petroleum ether extract completely inhibited the development of P. italicum under both storage periods, and no phytotoxic effects were recorded on citrus fruit.

CONCLUSIONS

This study demonstrates that plant extracts have a high potential to control blue mould of citrus and will provide a starting point for discovering new compounds with better activity than chemical fungicides currently available. Such natural products therefore represent a sustainable alternative to the use of chemical fungicides.