Antifungal activity of plant extracts against tomato’s fungal diseases

Abstract

Fungal diseases have always been a major problem for tomato crops. Growers generally use chemical fungicides to treat this type of diseases. However, these products are toxic to the environment and the consumer, especially if the pre-harvest interval is not respected. The present study aims to find non-polluting alternatives. Five plant extracts ( Peganum harmala, Ocimum basilicum, Caralluma europaea, Nerium oleander and Eucalyptus globulus ) are tested for their in vitro efficiency against four pathogenic fungi: Alternaria solani, Botrytis cinerea, Botrytis cinerea taken from fruit, Phytophthora infestans and Oïdium oxysporum . The obtained results reveal that the extract of Ocimum basilicum is the most effective on the studied fungi. Indeed, at a concentration of 0.4%, it inhibited at 80% the development of Botrytis cinerea and at 81% Oïdium oxysporum at a concentration of 0.2%. Followed by Peganum harmala and Nerium oleander , which also showed an antifungal effect ( Peganum harmala inhibited up to 73% of the growth of Alternaria solani at a dose of 4%). The extracts of Caralluma europaea and Eucalyptus globulus proved similar antifungal activity, which exceeded 30%. The study of the fungal/fungistatic effect revealed that all the studied extracts have a fungal effect against the treated fungi. The phytochemical screening showed that the plants extracts are rich in polyphenols especially Ocimum basilicum, Peganum harmala and Nerium oleander . This leads us to deduce that the antifungal activity may be due to this.