Induction of potato (Solanum tuberosum L.) defense genes by French marigold (Tagetes patula L.) essential oil

Abstract

When attacked, plants activate defense mechanisms including volatile emission. Besides having a pest repellent effect, volatiles can induce defense response in surrounding unharmed plants. French marigold (Tagetes patula L.) essential oil (EO) was isolated from the above-ground parts of plants collected from nature by hydrodistillation using Clevenger apparatus. GC/MS analysis revealed the presence of 42 compounds, of which 97% (32 compounds) have been identified. The monoterpene fraction was dominant (76.9%) with terpinolene (32.4%) and limonene (14.7%) as the most abundant compounds. In order to investigate the potential of marigold EO to induce the defense of potato, we analyzed 3 genes related to the induced resistance (IR): pathogenesis related PR-2 and PR-5 genes, and proteinase inhibitor Pin2. The potato plants were exposed to EO volatiles during 4, 8 and 12 h. Two leaves of EO-treated or untreated control plants were collected, and plants were then additionally injured by mechanically wounding leaves across the leaf surface. After 24 h of wounding, another two leaves from each plant were collected and expression of the IR related genes was analyzed by qPCR method. EO induced altered expression of PR genes, while Pin2 wasn’t affected by the treatment. Mechanical wounding increased the expression of all genes after 4 and 8 h of EO treatment, with up to 4-fold change in PR-2. However, in plants exposed to EO for 12 h before wounding, the level of transcription in PR-2 and Pin2 was similar to that detected in untreated controls. These findings support the efforts for environmentally-safe pest control in crops by using natural compounds.