Summary
The postharvest diseases of citrus fruit cause considerable losses during storage and transportation. These diseases are managed principally by the application of synthetic fungicides. However, the increasing concern for health hazards and environmental pollution due to chemical use has required the development of alternative strategies for the control of postharvest citrus diseases. Management of postharvest diseases using microbial antagonists, natural plant‐derived products and Generally Recognized As Safe compounds has been demonstrated to be most suitable to replace the synthetic fungicides, which are either being banned or recommended for limited use. However, application of these alternatives by themselves may not always provide a commercially acceptable level of control of postharvest citrus diseases comparable to that obtained with synthetic fungicides. To provide more effective disease control, a multifaceted approach based on the combination of different postharvest treatments has been adopted. Actually, despite the distinctive features of these alternative methods, several reasons hinder the commercial use of such treatments. Consequently, research should emphasize the development of appropriate tools to effectively implement these alternative methods to commercial citrus production.
Aims: The aim of this work was to find an alternative to the chemical fungicides currently used in the control of Geotrichum candidum, the causal agent of citrus sour rot.
Methods and Results: Minimal inhibition concentrations (MIC) and minimal fungicidal concentrations (MFC) were determined using agar dilution method. The methanol extracts of Cistus villosus, Ceratonia siliqua and Halimium umbellatum exhibited strong antifungal activity with MIC values ranged between 0·156 and 1·25 mg ml−1, and MFC values ranged between 2·5 and 5 mg ml−1. Incidence of sour rot was lowered to 0·00, 3·33 and 11·66% when mandarin fruit was treated with C. villosus, C. siliqua and H. umbellatum methanol extracts at 50 mg ml−1, respectively, compared with 95% in the control.
Conclusions: Cistus villosus, C. siliqua and H. umbellatum methanol extracts successfully reduced the disease incidence caused by G. candidum, and no phytotoxic effects were recorded on citrus fruit.
Significance and Impact of the Study: These findings suggest that C. villosus, C. siliqua and H. umbellatum plants may be useful and effective agents for control of citrus sour rot. Such natural products therefore represent a sustainable alternative to the use of synthetic fungicides.
The methanol Cistus extracts had sufficient antifungal activities in vitro and in vivo against G. citri-aurantii to consider its use in the citrus industry after it has been tested under production and natural infection conditions. Such natural products therefore represent a viable alternative approaches for sour rot postharvest management of citrus.
Significance and Impact of the Study: 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.
AbstractThe 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 25Á83 and 28Á33 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 (27Á50 mm) and the lowest MIC (1 mg ml À1 ). 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.
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