Journal
PHYTOPATHOLOGY
Volume 97, Issue 12, Pages 1558-1567Publisher
AMER PHYTOPATHOLOGICAL SOC
DOI: 10.1094/PHYTO-97-12-1558
Keywords
embolism; host water relations; sudden oak death; vascular disease
Categories
Ask authors/readers for more resources
Isolation, detection with diagnostic polymerase chain reaction (PCR), and microscopy demonstrated the presence of Phytophthora ramorum in the sapwood of mature, naturally infected tanoak (Lithocarpus densiflorus) trees. The pathogen was strongly associated with discolored sapwood (P < 0.001), and was recovered or detected from 83% of discolored sapwood tissue samples. Hyphae were abundant in the xylem vessels, ray parenchyma, and fiber tracheids. Chlamydospores were observed in the vessels. Studies of log inoculation indicated that R ramorum readily colonized sapwood from inoculum placed in the bark, cambium, or sapwood. After 8 weeks, radial spread of R ramorum in sapwood aver-aged 3.0 to 3.3 cm and axial spread averaged 12.4 to 18.8 cm. A field study was conducted to determine if trees with infected xylem had reduced sap flux and reduced specific conductivity relative to noninfected control trees. Sap flux was monitored with heat-diffusion sensors and tissue samples near the sensors were subsequently tested for P ramorum. Adjacent wood sections were excised and specific conductivity measured. Both midday sap flux and specific conductivity were significantly reduced in infected trees versus noninfected control trees. Vessel diameter distributions did not differ significantly among the two treatments, but tyloses were more abundant in infected than in noninfected trees. Implications for pathogenesis, symptomology, and epidemiology are discussed.
Authors
I am an author on this paper
Click your name to claim this paper and add it to your profile.
Reviews
Recommended
No Data Available