Presentation Title

Hydraulic Mechanisms of Fungal-Induced Dieback in a Keystone Chaparral Species during Unprecedented Drought in California

Presentation Type

Poster

Keywords

climate change, pathology, Laural Sumac, chaparral, fungi, water potential, hydraulic conductance

Department

Biology

Major

Biology

Abstract

Between 2012-2016, southern California experienced unprecedented drought that caused dieback in Malosma laurina, a keystone species of chaparral shrub communities. Dieback was especially severe in coastal exposures of the Santa Monica Mountains, leading to whole plant mortality exceeding 50% at some sites. We hypothesized that the endophytic fungus causing the dieback, Botryosphaeria dothidea, was successful in invading the xylem tissue of M. laurina because of protracted water stress, carbon starvation, or a combination of the two. We tested these possibilities in a controlled pot experiment by comparing three treatments, each inoculated with the fungus: (1) irrigated controls (2) non-irrigated (water stressed) plants and (3) carbon starved plants. We also compared the tissue dehydration limits of the chaparral host (M. laurina) to the fungal pathogen (B. dothedia) on culture media and living stem segments in the lab. Fungal elongation rates in xylem tissue of potted plants continued in all treatments over an eight-week period but were over two fold greater in water stressed plants than irrigated controls, leading to increased incidence of whole branch dieback. Minimum water potentials at the time of whole plant death and vulnerability to water stress-induced embolism of xylem conduits indicated that the host plant could not survive water potentials more negative than – 4 MPa. Stem segments in the lab at decreasing water potentials indicated continued rapid fugal elongation well below -4 MPa. These results were consistent with field observations of fungal blockage in water transport of xylem leading to branch dieback and eventual whole plant mortality.

Faculty Mentor

Dr. Stephen D. Davis

Funding Source or Research Program

Not Identified

Location

Waves Cafeteria

Start Date

24-3-2017 2:00 PM

End Date

24-3-2017 3:00 PM

This document is currently not available here.

Share

COinS
 
Mar 24th, 2:00 PM Mar 24th, 3:00 PM

Hydraulic Mechanisms of Fungal-Induced Dieback in a Keystone Chaparral Species during Unprecedented Drought in California

Waves Cafeteria

Between 2012-2016, southern California experienced unprecedented drought that caused dieback in Malosma laurina, a keystone species of chaparral shrub communities. Dieback was especially severe in coastal exposures of the Santa Monica Mountains, leading to whole plant mortality exceeding 50% at some sites. We hypothesized that the endophytic fungus causing the dieback, Botryosphaeria dothidea, was successful in invading the xylem tissue of M. laurina because of protracted water stress, carbon starvation, or a combination of the two. We tested these possibilities in a controlled pot experiment by comparing three treatments, each inoculated with the fungus: (1) irrigated controls (2) non-irrigated (water stressed) plants and (3) carbon starved plants. We also compared the tissue dehydration limits of the chaparral host (M. laurina) to the fungal pathogen (B. dothedia) on culture media and living stem segments in the lab. Fungal elongation rates in xylem tissue of potted plants continued in all treatments over an eight-week period but were over two fold greater in water stressed plants than irrigated controls, leading to increased incidence of whole branch dieback. Minimum water potentials at the time of whole plant death and vulnerability to water stress-induced embolism of xylem conduits indicated that the host plant could not survive water potentials more negative than – 4 MPa. Stem segments in the lab at decreasing water potentials indicated continued rapid fugal elongation well below -4 MPa. These results were consistent with field observations of fungal blockage in water transport of xylem leading to branch dieback and eventual whole plant mortality.