In vitro and in vivo antifungal activity of several Moroccan plants against Penicillium italicum, the causal agent of citrus blue mold

The aim of this study was to evaluate the antifungal activity of 50 plant species collected in different regions of southern Morocco against Penicillium italicum, the causal agent of citrus blue mold. The in vitro antifungal activity of plant powders was determined using the agar plate method. Our results showed that among the 50 plant species tested, the powders of Anvillea radiata and Thymus leptobotrys completely inhibited mycelial growth of P. italicum, at a concentration of 10% (w v−1). Furthermore, the powders of Asteriscus graveolens, Bubonium odorum, Ighermia pinifolia, Inula viscosa, Halimium umbellatum, Hammada scoparia, Rubus ulmifolius, Sanguisorba minor and Ceratonia siliqua were also effective against P. italicum with the inhibition of mycelial growth greater than 75%. The effect of plant aqueous extracts on spore germination varied significantly (P < 0.05) between tested plants. Aqueous extracts from A. graveolens, B. odorum and H. umbellatum totally inhibited germination of P. italicum conidia at a concentration of 10 mg ml−1. The most active plants in in vitro studies were tested in vivo against blue mold on citrus fruit. Incidence of blue mold was significantly lowered to 5 and 25% when orange fruit were treated with H. umbellatum and I. viscosa aqueous extracts, compared with 98% in the control. These results indicate that the plant powders contained compounds with antifungal potential against P. italicum. Such natural products may represent a sustainable alternative to the use of chemical pesticides.

► Anvillea radiata and Thymus leptobotrys plants completely inhibited mycelial growth of Penicillium italicum.
► Aqueous extracts from Asteriscus graveolens, Bubonium odorum and Halimium umbellatum totally inhibited germination of P. italicum conidia.
► Incidence of blue mold was lowered to 5 and 25% when orange fruit were treated with H. umbellatum and Inula viscosa extracts.
► The severity of disease varied from 5.22% (H. umbellatum) to 54.78% (B. odorum).