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Screening of Tobacco Genotypes for Phytophthora nicotianae Resistance
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Susceptibility in Viburnum to Phytophthora ramorum
Niklaus J Grünwald1, Megan Kitner1, Virginia McDonald2
1Horticultural Crops Research Laboratory, USDA ARS, 3420 NW Orchard Ave., Corvallis, OR 97330.
Plant Disease
|February 17, 2019
Summary
Phytophthora ramorum susceptibility varies greatly among Viburnum ornamental shrubs. This study found significant differences in leaf-based resistance, with some Viburnum genotypes showing high susceptibility to this emerging pathogen.
Area of Science:
- Plant pathology
- Horticultural science
- Forestry
Background:
- Phytophthora ramorum causes sudden oak death and Ramorum blight.
- Viburnum, a popular ornamental shrub genus, is known to be susceptible to P. ramorum.
- The susceptibility range within the Viburnum genus is not well understood.
Purpose of the Study:
- To determine if Viburnum cultivars differ in their susceptibility to Phytophthora ramorum.
- To assess the range of P. ramorum resistance within the Viburnum genus.
Main Methods:
- Controlled, detached leaf inoculations were performed.
- Two P. ramorum isolates from distinct clonal lineages in Oregon were used.
- Susceptibility was evaluated based on lesion development on leaves.
Main Results:
- Significant differences in susceptibility to P. ramorum were observed among Viburnum genotypes.
- Viburnum × burkwoodii, V. plicatum 'Mariesii', and V. lentago showed the highest susceptibility.
- Most evaluated Viburnum cultivars exhibited low susceptibility or resistance in detached leaf assays.
Conclusions:
- The Viburnum genus displays considerable variation in susceptibility to P. ramorum infection.
- Leaf-based assays indicate differential resistance within Viburnum cultivars.
- Field-based epidemic potential cannot be inferred solely from detached leaf resistance data.
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