Submitted to: Journal of Plant Physiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/9/2010
Publication Date: 6/15/2011
Publication URL: http://hdl.handle.net/10113/50279
Citation: Piesik, D., Panka, D., Delaney, K.J., Skoczek, A., Lamparski, R., Weaver, D.K. 2011. Cereal crop volatile organic compound induction after mechanical injury, beetle herbivory (Oulema spp.), or fungal infection (Fusarium spp.). Journal of Plant Physiology. 168(9): 878-886. Interpretive Summary: Insect herbivory and infection by necrotrophic fungal pathogens on plants can trigger similar plant defense response pathways. Here, we study plant volatile organic compound induction (VOC) responses to two beetle species (Oulema), three necrotrophic fungal pathogens (Fusarium), and five types of mechanical injury that simulate insect stem-mining or defoliation injuries. We study VOC responses of three cereal crops (barley, oat, and spring wheat) to examine similarities and differences to the 10 injury treatments. We found that the 5 mechanical injury treatments induced a few terpene VOCs with all three grasses, with one additional VOC from wheat and barley not induced from oat. However, beetle feeding and pathogen infection induced several additional VOCs compared to mechanical injury. Beetle feeding only induced one additional VOC that was not induced by Fusarium spp. infection. Different VOC blends were induced between the two beetle species, and between the three fungal pathogens, with overlap in concentrations of individual compounds. We caution that these results are preliminary because the grass*injury treatment combinations could not have VOCs collected simultaneously, due to the large number of treatments studied. This work suggests that injury by actual herbivores and fungal pathogens triggers more VOCs than mechanical injury. Most VOC differences between beetle herbivory and fungal pathogen infection were quantitative, but still might provide natural enemies information concerning the identity of the plant being attacked and the organism injuring the plant; future studies would need to test the latter. Our findings are part of an effort to understand how pest attack on crop plants relates to VOC production, and whether plant VOCs can be used in IPM to deter plant pests and/or to attract natural enemies of the pests.
Technical Abstract: Herbivory, mechanical injury or pathogen infestation to vegetative tissues can induce volatile organic compounds (VOCs) production, which can provide defensive functions to injured and uninjured plants. In our studies with ‘McNeal’ wheat, ‘Otana’ oat, and ‘Harrington’ barley, plants that were mechanically injured, attacked by either of two Oulema spp. (melanopus or cyanella) beetles, or infected by one of three Fusarium spp. (graminearum, avenaceum, or culmorum), had significant VOC induction compared to undamaged plants. Mechanical injury to the main stem or one leaf caused the induction of one green leaf volatile (GLV)- (Z)-3-hexenol, and three terpenes ('-linalool, '-caryophyllene, and '-pinene) with all three grasses; wheat and barley also had '-linalool oxide induction. The blend of induced VOCs after Fusarium spp. infestation or Oulema spp. herbivory was dominated by GLVs ((Z)-3-hexenal, (E)-2-hexenal, (E)-2-hexenol, (Z)-3-hexenyl acetate, and 1-hexenyl acetate) and '-linalool and '-caryophyllene; beetle herbivory also induced (E)-ß- farnesene. Different ratios of individual VOCs were induced between the two Oulema spp. for each cereal grass and different ratios across the three cereals for each beetle species. Also, different ratios of individual VOCs were induced between the three Fusarium spp. for each cereal grass and different ratios across the three cereals for each fungal pathogen species. Our results are preliminary since we could not simultaneously measure VOCs induction from controls with each of the ten different injury treatments for each of the three cereals. However, the comparison of mechanical injury, insect herbivory, and fungal infection has not been previously examined with VOCs responses from three different plant species within the same family. Also, our work suggests large qualitative and quantitative overlap of VOC induction from plants of all three cereals having beetle herbivory injury when compared to infection injury from necrotrophic fungal pathogens.