Obtention and sequential selection of antifungal pomegranate (Punica granatum L. cv. ‘Mollar de Elche’) peel extracts to control postharvest decay of citrus fruits caused by Penicillium spp.

• ‘Mollar de Elche’ peel extracts were obtained with different solvents and procedures • PPEs were sequentially evaluated for citrus green and blue molds control • The best were a methanolic and a water PPE, at 12 g/l dry residue and 70 mL/L DMSO • A mixture of these PPEs did not improve their individual effectiveness • A 150-s dip treatment with these PPEs showed potential for mold commercial control Green and blue molds, caused respectively by Penicillium digitatum and Penicillium italicum, are the most economically important postharvest diseases of citrus fruits. Although synthetic chemical fungicides are used for their control, nonpolluting control methods, such as the application of natural antifungal plant extracts, are increasingly required. In this work, different ‘Mollar de Elche’ pomegranate peel extracts (PPEs) were obtained and sequentially evaluated for the control of these diseases. The extracts were obtained with different solvents and their curative activity was evaluated in in vivo primary screening tests. For this, single extracts or combinations of them were applied at different concentrations to different cultivars of oranges and mandarins artificially inoculated with P. digitatum 24 h before extract application and incubated at 20°C. Aqueous solutions of the best extracts were then evaluated in small-scale dip treatments, and immersion times of 150 s were selected as the most effective in reducing the incidence and severity of green and blue molds. Among a wide range of extraction methods and solvents used, the most effective extracts were those obtained with water (Wat-SP PPE) and methanol (Met PPE), at concentrations of 12 g L -1 dry residue supplemented with 70 mL L -1 of dimethyl sulfoxide (DMSO). This solvent increased the antifungal activity of some PPEs, but did not reduce disease when applied as a single treatment. In further trials, Met PPE and Wat-SP PPE reduced the incidence of green mold by 39 and 52 % and that of blue mold by 30 and 48 %, respectively, on ‘Clemenules’ mandarins after 4 weeks of storage at 5 °C. The results of this study contribute to the valorization of pomegranate waste and by-products and represent a significant advance in the development of natural, effective, and environmentally friendly antifungal treatments to reduce postharvest diseases of citrus fruits.