Integrated control of postharvest Fusarium solani of potatoes using UV-C irradiation and Moringa oleifera leaf extracts.

Abstract

Potatoes are a source of food, income and important nutrients which are beneficial to human health. However, production of potato tuber may be hindered by postharvest losses, which reduce the quality and quantity of potatoes reaching consumers. Major losses of potatoes are caused by poor harvesting, sorting, cleaning, handling, and packing. Fusarium solani, a causal agent of dry rot disease that mainly affects potatoes occurs during storage as the pathogen invades the potato tuber through tissue injuries inflicted during lifting or grading. Fusarium dry rot has been mainly controlled by using chemicals. However, the frequent use of chemicals has been recently reported to enhance fungicide resistance to potato pathogens. Chemical fungicides also negatively affect human health and the environment, as they introduce residues in treated potatoes and soil. There is a need to investigate and develop sustainable agricultural strategies such as UV-C irradiation and plant extracts as alternative strategies which are human and environmentally friendly. Therefore, this research aimed to evaluate the effect of UVC irradiation and Moringa oleifera leaf extract, independently and their combined effect in controlling F. solani on potatoes in vitro and in vivo. The antifungal effects of UV-C irradiation against F. solani were evaluated in vitro and in vivo. UV-C treatment for 10 and 15 minutes at a 10 cm distance successfully inhibited the mycelial growth of F. solani by ≥ 50% at 7-day post-inoculation. The in vivo results showed that ‘Sifra’ potatoes treated with UV-C for 10 minutes and 15 minutes had a disease incidence ≤ 33%. The increase in the duration of UV-C exposure to potatoes lowered the disease incidence on potatoes. The scanning electron icrographs showed the breakage and shrinkage of the mycelia in vitro, and the disruption of spores in UVC -treated potatoes. Moringa leaf extracts were prepared and adjusted into different concentrations, MLE 1%, MLE 1.5%, MLE 2%, MLE 2.5%, and MLE 3%. These concentrations were evaluated for their efficacy against F. solani in vitro and in vivo. The findings demonstrated that MLE 1.5%, MLE 2.5%, and MLE 3% inhibited the mycelial growth of F. solani by ≥ 50% in vitro. The in vivo findings revealed that both MLE 2.5% and MLE 3% reduced incidence of dry rot in potatoes. The antifungal activity of moringa was increased at higher concentrations. The scanning electron micrographs showed mycelia distortion in samples treated with moringa and the disruption of F. solani spores on the treated potatoes. It also indicated the formation of biofilms in moringatreated potatoes. Furthermore, this study evaluated the effect of integrated control of F. solani using UVC and moringa leaf extracts. The in vitro results demonstrated that samples treated with MLE 2.5% and exposed to UV-C for 15 minutes inhibited the mycelial growth of F. solani by 100%. ‘Sifra’ potatoes exposed to UV-C for 15 minutes and treated with MLE 3% had the lowest disease incidence (8.33%). The scanning electron micrographs showed abnormal, shrinkage, disruption, aggregation and reduced hyphae length of mycelia in samples treated with both UV-C and MLE. Moreover, it indicated the formation of biofilms in UV and moringa-treated surfaces of potato wounds. These integrated treatments enhanced efficacy compared to the individual application of either treatment. UV-C can be integrated with moringa and be used as alternatives to synthetic fungicides to control dry rot of potatoes.