In Vitro antifungal activity of selected GRAS salts against postharvest fungal pathogens of 𝘊𝘢𝘱𝘴𝘪𝘤𝘶𝘮 𝘢𝘯𝘯𝘶𝘶𝘮 (Banana Pepper)

Abstract

Banana pepper (𝘊𝘢𝘱𝘴𝘪𝘤𝘶𝘮 𝘢𝘯𝘯𝘶𝘶𝘮 𝘓.) is an economically important vegetable crop grown worldwide. Fungal diseases cause substantial postharvest losses of banana pepper. This study investigated the effect of Generally-Recognised-As-Safe (GRAS) salts; calcium chloride (CaCl₂) and potassium silicate (K₂SiO₃), on in vitro growth of postharvest fungal pathogens, 𝘊𝘰𝘭𝘭𝘦𝘵𝘰𝘵𝘳𝘪𝘤𝘩𝘶𝘮 sp., 𝘍𝘶𝘴𝘢𝘳𝘪𝘶𝘮 sp., 𝘈𝘴𝘱𝘦𝘳𝘨𝘪𝘭𝘭𝘶𝘴 sp., 𝘓𝘢𝘴𝘪𝘰𝘥𝘪𝘱𝘭𝘰𝘥𝘪𝘢 sp. and 𝘗𝘦𝘴𝘵𝘢𝘭𝘰𝘵𝘪𝘢 sp., isolated from banana pepper. The direct inhibitory effect of GRAS salts on pathogen growth was tested by assessing radial growth on GRAS salt-amended potato dextrose agar (PDA) and mycelial growth in static cultures of potato dextrose broth (PDB) at 1% CaCl₂ and 800 mg L⁻¹ K₂SiO₃ concentrations with three replicates. Effect of GRAS salts on spore germination of pathogens was also tested. Treatments with CaCl₂ and K₂SiO₃ did not significantly (𝘱 < 0.05) reduce the pathogen growth in either PDA or PDB while CaCl₂ treatment exhibited a stimulatory effect on radial growth (cm) of 𝘊𝘰𝘭𝘭𝘦𝘵𝘰𝘵𝘳𝘪𝘤𝘩𝘶𝘮 sp., 𝘍𝘶𝘴𝘢𝘳𝘪𝘶𝘮 sp. and 𝘗𝘦𝘴𝘵𝘢𝘭𝘰𝘵𝘪𝘢 sp. (5.8, 5.5 and 8.5, respectively) versus their controls (5.1, 2.7 and 7.5, respectively). Treatment with CaCl₂ significantly reduced the spore germination of 𝘍𝘶𝘴𝘢𝘳𝘪𝘶𝘮 sp. (by 37.48%) and 𝘈𝘴𝘱𝘦𝘳𝘨𝘪𝘭𝘭𝘶𝘴 sp. (by 67.21%) while K₂SiO₃ treatment significantly reduced the spore germination of Fusarium sp. (by 52.77%) against controls. The differential effects observed suggest that the efficacy of CaCl₂ and K₂SiO₃ be influenced by the specific fungal species, their developmental stage, or potential chemical interactions between calcium and silicate ions with other constituents present in PDB and PDA media. Notably, both calcium and silicate solutions, when prepared in sterile distilled water, exhibited antifungal activity, as demonstrated by the spore germination assay. These observations highlight the need for further 𝘪𝘯 𝘷𝘪𝘷𝘰 investigations to gain a clearer understanding of the effects of these GRAS salts on the growth of the tested postharvest pathogens.