Evaluation of antifungal properties of medicinal plant extracts against post-harvest diseases

Abstract:

Growers in the West African farmers have reached for neem twigs and clove water to slow fruit rot for nearly two hundred years, yet the underlying chemistry has only recently been aligned with modern mycological endpoints. This research tested methanolic extracts of four medicinal plants - neem (Azadirachta indica), tulsi (Ocimum sanctum), ginger (Zingiber officinale) and clove (Syzygium aromaticum) - against three economically damaging post-harvest pathogens: Colletotrichum gloeosporioides, Botrytis cinerea and Penicillium digitatum. Poisoned food assays and spore germination tests were conducted between August 2022 and April 2023 at the University of Nigeria, Nsukka, Enugu State. Clove extract emerged as the most potent, with EC₅₀ values of 184, 216 and 249 µg mL⁻¹ against the three pathogens respectively, followed by ginger (EC₅₀ 287–342 µg mL⁻¹), neem (413–486 µg mL⁻¹) and tulsi (498–576 µg mL⁻¹). At 2000 µg mL⁻¹, clove extract held spore germination of C. gloeosporioides to 18.7 percent against 93.7 percent in the untreated control over 24 hours. Scanning electron microscopy of treated hyphae showed clear cell wall disruption and membrane collapse, agreeing with the leakage of 260 nm absorbing material measured photometrically. In-planta trials on harvested mango and grape fruits showed that a 1500 µg mL⁻¹ clove extract dip cut the disease incidence by 71.4 percent over eight days. The results support botanical extracts - clove in particular - as credible additions to the post-harvest tool kit, especially in organic and smallholder settings.