Application of Selected Plant Extracts to Inhibit Growth of Penicillium expansum on Apple Fruits

Penicillium expansum is an important postharvest pathogen that not only causes decay on apple and pear fruit but also produces the carcinogenic mycotoxin patulin in spoiled fruit and processed fruit. Although synthetic fungicides are effective to protect against fruit decay, their potential effects on human health and the environment are a concern. Plant extracts are one of several non-chemical control alternatives that inspiring great interest due to their availability, non-toxicity and friendliness to the environment. In this study, screening of antifungal activity against P. expansum from sixteen plants (garlic, clove, dokudami, kumasasa, dandelion, kusagi, yomogi, ginkgo, marigold, lavender, thyme, hot pepper, ginger and lemon basil) by means of solvent extraction with either dichloromethane or diethyl ether was conducted. By the solution contact method and the vapor contact method, plant extraction of 16 plants was treated on PDA and the diameter of a clear inhibition zone was recorded daily for 5 d. Next, 100 L of conidia suspension was added to each wound on apple fruits. Lesion diameter of the treated fruits was observed daily for 6 d. The antifungal activity against P. expansum of garlic, thyme, lavender, ginkgo and dandelion which directly contacted the fungal spore, was distinguishingly affective with a clear inhibition zone diameter higher than 12 mm over 5 days of incubation. Apple fruits were treated with garlic extracts by the solution contact method. Growth inhibition activity of P. expansum in an amount of 50 L was higher than that in 20 L which was equally effective control. Apples exposed to vapor of garlic extract at 1, 2 and 3 ml L-1 for 24, 48 and 72 h show different antifungal effects on P. expansum. Vapor contact of Allium sativum at a concentration of 1 ml L-1 with 72 h of exposure time demonstrated the most optimal performance in terms of fruit appearance. In these results, dichloromethane is an appropriate solvent for use in extracting active compounds from plants presenting antifungal activity against P. expansum. Crude extract of garlic was the most effective, both in the form of solution and vapor contact, for inhibiting mycelium growth of P. expansum. In addition, garlic extract is applicable at relatively low concentration to reduce blue mold rot on apple fruits.