Allelopathic effects of root exudates of grafted eggplants on Verticillium dahliae and their constituents’ identification

We tested the occurrence and severity of Verticillium wilt in grafted eggplants. The root exudates of grafted eggplants were collected with root soaking method. Their constituents were determined by gas chromatography/mass spectrometry (GC/MS) and the effects of root exudates were evaluated on the mycelial growth of Verticillium dahliae. Dibutyl phthalate (DP), hexadecanoic acid (HA) and tetradecanoic acid (TA) detected in natural root exudates from eggplants were chosen to test their biological activities against Verticillium dahliae. The grafted eggplants showed less disease incidence of Verticillium wilt. With the development of plants, the quantity of V. dahliae in soil was lower in grafted eggplants than in non-grafted eggplant. The root exudates were more inhibitory to mycelial growth in grafted eggplants than in non-grafted eggplants. Grafting changed the constituents of the root exudates of eggplants. In root exudates of grafted eggplants, hydrocarbons, esters, alcohols, phenols, ketones, benzenes and amine were present, while, in non-grafted eggplants alcohols, benzenes and amine were absent. The compounds present in the root exudates were also found in soil extracts and also observed the similar trend in their contents. The inhibitory effects of DP on mycelial growth of V. dahliae increased at lower concentration, but was decreased at higher concentration. The inhibitory activities of HA and TA were decreased at lower concentration, but increased at higher concentration.