Interacting elevated CO 2 and tropospheric O 3 predisposes aspen ( Populus tremuloides Michx.) to infection by rust ( Melampsora medusae f. sp. tremuloidae )

Abstract

We investigated the interaction of elevated CO 2 and/or (Ozone) O 3 on the occurrence and severity of aspen leaf rust ( Melampsora medusae Thuem. f. sp. tremuloidae ) on trembling aspen ( Populus tremuloides Michx.). Furthermore, we examined the role of changes in leaf surface properties induced by elevated CO 2 and/or O 3 in this host–pathogen interaction. Three‐ to five‐fold increases in levels of rust infection index were found in 2 consecutive years following growing‐season‐long exposures with either O 3 alone or CO 2 + O 3 depending on aspen clone. Examination of leaf surface properties (wax appearance, wax amount, wax chemical composition, leaf surface and wettability) suggested significant effects by O 3 and CO 2 + O 3 . We conclude that elevated O 3 is altering aspen leaf surfaces in such a way that it is likely predisposing the plants to increased infection by aspen leaf rust.

Bibliographic Information