Document: AND-3-55-7
Interactive effects of drought stress and infection by Xylella fastidiosa on the ecophysiology of a common liana.
MCELRONE, A.J.* and I.N.FORSETH
University of Maryland, College Park, MD 20742 USA 1
Abstract:
Recent work by ecologists has shown that plant pathogens can have substantial impacts on natural communities. However, there is still a need to know how disease is modified by concurrent abiotic factors. We used a greenhouse experiment to examine the interactive effects of drought stress and disease infection by the common, xylem-limited bacteria Xylella fastidiosa on the ecophysiology of a liana, Parthenocissus quinquefolia. A 2 by 2 complete factorial design with two water treatments (high, HW and low, LW) and two infection treatments (control and inoculated) was used to test the hypothesis that disease symptoms are more severe and progress more quickly during periods of drought stress. Leaf scorch symptoms and several water-relations parameters were analyzed at five leaf positions along the vine. Symptoms progressed further along the stem in low water-inoculated plants (LI) as compared to high water-inoculated plants (HI). Scorch symptoms were very severe in the LI treatment with nearly 40% of the leaf area exhibiting scorching, compared to only 8% for HI at a corresponding basal leaf position. Stomatal conductance was lower for LW plants at all leaf positions and was significantly reduced for HI at the most basal leaf position compared to controls. A significant water by infection interaction was found for basal leaf water potentials with LI plants lower than all other treatments throughout the day. Stem hydraulic conductivity was significantly reduced by both LW and infection treatments. These results suggest that the LW treatment speeds the progression of the pathogen as it advances towards the shoot apex.
Keywords: drought, xylem-limited plant pathogen, ecophysiology, water-relations
This abstract is being presented at: 3:30 PM in session:
Poster Session #17: Vegetative Analysis.