S14 - Session O2 - Garlic Volatile Diallyl Disulfide Induced Cucumber Resistance to Downy Mildew

Authors: Zhihui Cheng *, Fan Yang

Allicin compositions in garlic are used widely as fungicides in modern agriculture, in which diallyl disulfide (DADS) is a major allelochemical compound. Downy mildew, caused by Pseudoperonospora cubensis , is one of the most destructive diseases and causes severe yield losses in cucumber production. To explore the potential mechanism of DADS-induced cucumber resistance to downy mildew, cucumber seedlings were treated with DADS and then inoculated with P. cubensis at a 10- day interval, then phenotypic observation and physiological changes were performed to reveal the infection processes and cucumber resistance responding mechanisms to the infection of P. cubensis. Symptom observation showed that DADS significantly induced cucumber resistance to downy mildew. Furthermore, both lignin and H 2 O 2 were significantly increased by DADS treatment to responding P. cubensis infection. Simultaneously, the enzyme activities of peroxidase (POD) in DADS-treated seedlings were significantly promoted. Meanwhile, both the auxin (IAA) and salicylic acid (SA) contents were increased when treated with DADS. The results of this study might give new insight into the exploration of the induced resistance mechanism of cucumber to downy mildew. Additionally, this work might provide an alternative environmentally friendly way for reducing the continuous cropping obstacles and controlling leaf diseases during the cultivation of vegetables.