Effects of plant-fungal interactions on volatile emission of Hordeum vulgare and aphid preference

Abstract: Barley is one of the most economically important cultivated crops in the world. However, barley is a host for many insect pests and plant pathogenic fungi which is a threat to the production. Rhopalosiphum padi is an economically important insect pest that leads to large economical losses in agricultural crops such as barley. An increased understanding of interactions between insects, plants and microorganisms is an important step in developing non-chemical control strategies to prevent major outbreaks of aphids and other pests. This study firstly aims to study the effect of barley inoculated with the beneficial fungi Trichoderma atroviride and the plant pathogen Fusarium graminearum on emission of volatile organic compounds. Secondly, it aims to analyse aphid behavior and preference to odours from barley plants inoculated with T. atroviride, F. graminearum and non-inoculated controls through olfactometer tests. Volatile organic compounds were collected on volatile traps from barley-plants inoculated and grown under controlled conditions in a growth chamber. The volatile organic compounds were analysed and quantified in a Gas chromatography – mass spectrometry (GC-MS) and then in the Automated Mass Spectral Deconvolution and Identification System (AMDIS). The result of the volatile analysis showed no significant differences in the total volatile organic compound (VOC) composition between plants inoculated with F. graminearum, T. atroviride and non-inoculated plants. The olfactometer test result shows no significant difference in aphid preference between plants inoculated with F. graminearum and non-inoculated plants. However, R. padi did significantly prefer non-inoculated plants over plants inoculated with T. atroviride. As a conclusion, based on the results in this study, VOCs induced by T. atroviride could possibly work as repellents for R. padi. However, further studies on the interaction between plants, insects and microorganisms are needed to develop new control strategies and possibly use it as biological control and in Integrated Pest Management (IPM).