In vitro control of Colletotrichum gloeosporioides, causal agent of anthracnose on grapefruit (Citrus paradisi), using plant extracts

Background/Objective. Citrus (Citrus spp.) production is affected annually by anthracnose, associated with Colletotrichum spp. This disease can occur preharvest and postharvest and is generally controlled with synthetic fungicides, which pose health problems for farmers and consumers, negatively impact the environment, and lead to the emergence of resistant phytopathogen populations. An alternative to these problems is the application of plant extracts with antifungal properties, which could contribute to the production of safe food. Therefore, the objective of this study was to evaluate the effect of plant extracts under in vitro conditions against Colletotrichum gloeosporioides, causal agent of anthracnose on grapefruit (Citrus paradisi). Materials and Methods. Extracts were obtained from 17 plant species. The effectiveness of the extracts was evaluated using the poisoned PDA culture technique (PDA + 10% plant extract), in which 5 mm diameter discs of the fungus were inoculated onto Petri dishes. The fungicide Benomyl (10%) was used as a positive control, and pure PDA as a negative control. A completely randomized experimental design with 19 treatments and three replicates was used. The percentage of inhibition of C. gloeosporioides mycelial growth was recorded when the negative control completely covered the surface of the Petri dish. Data were analyzed using the statistical software SAS version 9.0. Results. The best extracts were zopilote seed (Swietenia macrophylla), bull blood tree bark (Bocconia arborea), and bull blood tree leaf and stem (B. arborea), and moringa seed (Moringa oleifera), inhibiting the growth of C. gloeosporioides by 69.2, 67.5, 44.1, and 35.6%, respectively. The positive control, Benomyl, inhibited C. gloeosporioides growth by 100%. Conclusion: The best in vitro inhibitory effect on Colletotrichum gloeosporioides was obtained with Swietenia macrophylla seed extracts (69.2%), followed by Bocconia arborea bark (67.5%), B. arborea leaf and stem (44.1%), and Moringa oleifera (35.6%).