Interaction between abiotic and biotic stresses: salinity and herbivory in woody plants

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Salinity affects around 10 M ha of irrigated land in North America. In addition, in Canada mining has disturbed our ecosystems, resulting in areas of land with relatively high salt content, which must be reclaimed to support forest ecosystems. The presence of salts in the soil limits plant growth by reducing water uptake (osmotic stress), inducing ion (Na+ and Cl-) toxicity, causing nutrient imbalance as well as producing free radicals (oxidative stress). Although the development of molecular techniques has allowed the characterization of a large number of genes involved in stress response; our knowledge of the mechanisms of salinity tolerance of northern woody plants requires more research to select plants that can grow on salt-impacted soils in the boreal forest. Furthermore, to survive salinity stress, plants undergo physiological changes that alter the biochemical pathways involved in plant response to other stresses including biotic stress. Insect herbivory is a biotic stress that is a major concern in the Boreal forest and could cause further damage to our forest ecosystems with climate change. Our preliminary experiments on agricultural crop species suggest that the interaction between herbivory and salinity could vary depending on the salt tolerance of the plants and their nitrogen status. My research program proposes to combine physiological, biochemical and molecular techniques to conduct innovative research on the interaction between salinity and insect herbivory in woody plants for the Boreal forest. The objectives of the proposed research are 1) to determine if tolerance to salinity stress increases the ability of the plants to resist insect herbivore attack; 2) To study the role of the plant growth regulator, jasmonic acid (JA) in the interaction between salinity and herbivory. JA plays a key role not only in the response to herbivory to induce defense mechanisms (production of secondary compounds) but also in abiotic stress (drought and salinity). Could the change in JA level in response to salinity help the plant limit herbivory attack? 3) To determine if salt-induced changes in nitrogen (N) metabolism could affect insect herbivory resistance. Changes in N transport and assimilation under salinity stress could occur to counterbalance salt-induced nutrient imbalance depending on the salinity tolerance of the species and therefore potentially affect herbivory resistance. This research will be conducted under controlled conditions in a greenhouse by 10 students who will gain valuable expertise in environmental physiology. This research will complement existing research on northern ecosystems and will advance my research program on salt tolerance mechanisms and the interaction between stresses. It will also deliver tools that will help to develop strategies to reclaim successfully disturbed areas in the Boreal forest and limit the impact of human activities on the environment.