Antifungal activity of some Moroccan plants against Geotrichum candidum, the causal agent of postharvest citrus sour rot

The powders and aqueous extracts of 43 plant species, harvested in different regions of southern Morocco, were screened for their in vitro and in vivo antifungal activity against Geotrichum candidum, the cause of citrus sour rot. Our results show that among the 43 plants tested, the powders of Rubus ulmifolius, Ceratonia siliqua, Cistus monspeliensis and Halimium umbellatum plants totally inhibited mycelial growth of G. candidum. Furthermore, the powders of Cistus villosus, Pistacia atlantica, Halimium antiatlanticum, Inula viscosa, Ighermia pinifolia and Hammada scoparia plants are also effective against G. candidum with a percent of inhibition of mycelial growth higher than 80%. The effect of plant aqueous extracts on spore germination varied significantly (P < 0.05) between tested plants. Aqueous extracts from H. antiatlanticum and C. villosus plants showed the strongest activity. The first species completely inhibited the spore germination at 2.5 and 5 mg ml−1, and the second species at 5 mg ml−1. The most active plants in in vitro studies were tested in vivo against sour rot on citrus fruit. Incidence of sour rot was lowered to 44.44 and 46.30% when mandarin fruit were treated with C. villosus and H. antiatlanticum aqueous extracts, compared with 98.15% in the control. This study demonstrates that plants extracts have a high potential to control sour rot of citrus. Such natural products therefore represent a sustainable alternative to the use of chemical pesticides.

► Powders of Ceratonia siliqua and Halimium umbellatum totally inhibited growth of Geotrichum candidum.
► Halimium antiatlanticum and Cistus villosus fully inhibited the spore germination at 5 mg·ml−1.
► Best disease control when fruit where treated with C. villosus and H. antiatlanticum.
► Plant extracts could be used as a potential source of antifungal compounds.