Abstract
Blue mold caused by Penicillium italicum imposes a serious problem in economically important citrus fruit during the storage period. Traditionally, synthetic chemicals have been widely used to control blue molds; however, this use of chemicals has caused critical environmental problems. This has encouraged scientists to look for safer and readily available alternatives from natural eco-friendly sources such as botanical extracts. In line with that, the present study aims to investigate the antifungal efficiency of twelve methanolic extracts from eight plant species against P. italicum in vitro and to further select the most promising extracts to study their efficacy in vivo on reduction of disease severity and some physiological aspects of 'Washington Navel (c)' orange fruit under storage conditions. Being the most effective treatment, Sansevieria cylindrica leaf extract was subjected to GC-MS analysis to identify phytochemical components. The results obtained signified the potential efficacy of the tested plant extract to reduce the mycelial growth of P. italicum under in vitro conditions. The most effective extracts were Balanites aegyptiaca fruit, Polianthes tuberosa bulbs, Acacia nilotica fruit and Sansevieria cylindrica leaves at 1000 mu g/mL inhibition % of mycelial of 54.3, 42.4, 41.3 and 31.5%, respectively. When compared under storage conditions of orange fruit, the lowest disease incidence and, thus, the highest reduction of disease severity (86.7%) were caused by S. cylindrica leaf extract. These effects were supported by high values of total phenols content (TPC) and total flavonoids content (TFC) in treated fruit, along with elevated activities of antioxidant enzymes: peroxidase (PO) and polyphenol oxidase (PPO). The identified phytochemicals in S. cylindrica leaf extract were dominated by fatty acids and their esters, which, together with the other compounds, have evidence of microbial activity. To sum up, using methanolic extracts of S. cylindrica as a substitute for chemical fungicides may help control P. italicum in 'Washington Navel (c)' oranges.