Abstract Detail

Physiology

Garcia, Cristian M [1], Aguirre, Natalie M [2], Davis, Stephen [3].

Comparative Dehydration Tolerance between the Fungal Pathogen Botryosphaeria dothidea and Three Chaparral Host Species.

We tested the hypothesis that an opportunistic endophytic fungus Botryosphaeria dothidea continues to elongate and grow in host tissues at dehydration levels that exceed host survival. This is a hypothesis especially worthy of testing because Botryosphaeria dothidiea frequently infects and causes dieback in several different species of chaparral shrubs in the Santa Monica Mountains. We tested our hypothesis by collecting several large branches from the field from three dominant species of co-occurring chaparral shrubs, Malosma laurina, Ceanothus spinosus, and Ceanothus megacarpus. We allowed branches to dehydrate at increasing lengths of time, from a few days to one week, in an air-conditioned laboratory, then in plastic bags overnight to allow tissue-water equilibration, and thus measured water potential of stem tissues at different dehydration levels. Stem segments were then inoculated with the fungal pathogen B. dothidea, enclosed in test tubes with an air gap, and allowed to incubate for a total of six days. After six days of fungal growth, lengths of hyphal invasion into stem tissues were recorded and final water potentials were determined using a dew point hygrometer. In all three species, fungal elongation continued below the water potential thresholds for survival. In Malosma laurina (-5.3 MPa ± 1 SE, n = 30), exceeding the survival limits of the host plant (100% cavitation of stem xylem at -4 MPa). In Ceanothus spinosus (-8.5 MPa ± 1 SE, n = 30), exceeding the survival limits of the host at -8 MPa. In Ceanothus megacarpus (-13.2 MPa ± 1 SE, n = 30), also exceeding the survival limits of the host at -12 MPa. This indicates that the invasion and growth of the fungal pathogen B. dothidea in the stem xylem of these co-dominant chaparral species can continue under severe drought conditions recently experienced in California and likely contribute to the whole plant mortality increasingly observed for these species.

1 - Pepperdine University, Natural Science Division, 24255 Pacific Coast Hwy. #1424, Malibu, California, 90263-1424, United States
2 - Pepperdine University, Natural Science Division, 24255 Pacific Coast Hwy, Malibu, California, 90263, United States
3 - Pepperdine University, NATURAL SCIENCE DIV, 24255 Pacific Coast Highway, Malibu, CA, 90263, United States

Keywords:
Physiology.

Presentation Type: Poster
Session: P, Physiology Posters
Location: Arizona Ballroom/Starr Pass
Date: Monday, July 29th, 2019
Time: 5:30 PM This poster will be presented at 6:15 pm. The Poster Session runs from 5:30 pm to 7:00 pm. Posters with odd poster numbers are presented at 5:30 pm, and posters with even poster numbers are presented at 6:15 pm.
Number: PPS006
Abstract ID:857
Candidate for Awards:Physiological Section Best poster presentation,Physiological Section Physiological Section Li-COR Prize