Volatile-organic compound changes in rose twigs consequent to infection with rose powdery mildew

Fazhong Yang1, 2, Wenxia Dong1, Xiuge Zhang1, Yunxian Li2, Shiping Zhou2, Guolei Zhu2, and Chun Xiao1*
The chemical mechanisms involved in indirect plant-mediated interactions between insects and phytopathogenic fungi on the host plant are poorly understood. Fungus-induced changes in the volatile organic compound (VOC) contents of plants need to be elucidated to address this. Here, changes in VOCs in rose (Rosa chinensis Jacq.) leaves infected with rose powdery mildew (Podosphaera pannosa [Wallr.: Fr.] de Bary) were studied. VOCs were collected from undamaged live leaves of healthy and infected intact rose plants by dynamic headspace adsorption and identified by GC-MS. VOCs were extracted using n-hexane, and 38 chemicals were found to be produced by P. pannosa. A total of 71 VOCs not produced by P. pannosa were produced to different degrees by infected and healthy plants, and 18 of these were produced only by infected plants. Principal component analysis of chromatographic data gave VOC profiles distinguishing between infected and healthy plants. Hexadecanol, octadecanol, tetradecanol, n-butyl hexadecanoate, and n-butyl stearate dominated the VOCs produced by infected plants. These chemicals can be used as markers for detecting mildew-infected rose plants even 4-7 d after infection before symptoms appear. Clear temporal changes in the concentrations of these five chemicals were found. The results improve our understanding of the chemical mechanisms involved in interactions between insects and phytopathogenic fungi.
Keywords: Biomarker, GC-MS, hexadecanol, induced plant defense, Podosphaera pannosa, Rosa chinensis, semiochemicals, volatile organic compound.
1Yunnan Agricultural University, School of Plant Protection, Kunming 650201, Yunnan, P.R. China.
*Corresponding author (xiaochune@yeah.net).
2Southwest Forestry University, Key Laboratory of Forest Disaster Warning and Control of Yunnan Province, Kunming 650224, Yunnan, P.R. China.