Photosynthetic declines are induced by Phytophthora ramorum infection and exposure to elicitins

Abstract

Infection of compatible plants by Phytophthora spp. often leads to a decline in stomatal conductance and photosynthesis, although the mechanistic basis for such declines is not completely understood. In many cases, declines in leaf gas exchange rates have been linked to losses in water supply capacity associated with root and/or xylem. However, the reductions in gas exchange may not be proportional to changes in hydraulic capacity, and may be observed in non-invaded regions, suggesting the presence of a toxin, or host-derived signal, that is responsible for some of the physiological impairment.

In the current study, we first conducted a series of experiments to determine if toxins secreted by P. ramorum are likely contributors to physiological injury in the host by examining the temporal changes in photosynthesis, stomatal conductance, and hydraulic conductivity of Rhododendron macrophyllum G. Don (rhododendron) artificially inoculated with P. ramorum. Second, we tested the ability of culture filtrates and purified, recombinant P. ramorum elicitins (i.e., the major proteins secreted by P. ramorum grown in vitro) to induce physiological changes in incompatible Nicotiana tabacum (tobacco) and compatible tanoak, rhododendron, and Umbellularia californica (California bay laurel) host species.

Parent Publication

• Proceedings of the sudden oak death third science symposium

Citation

Manter, Daniel K.; Kelsey, Rick G.; Karchesy, Joseph J. 2008. Photosynthetic declines are induced by Phytophthora ramorum infection and exposure to elicitins. In: Frankel, Susan J.; Kliejunas, John T.; Palmieri, Katharine M., tech. coords. 2008. Proceedings of the sudden oak death third science symposium. Gen. Tech. Rep. PSW-GTR-214. Albany, CA: U.S. Department of Agriculture, Forest Service, Pacific Southwest Research Station. pp. 399-402