First report of Phytophthora inundata associated with a latent infection of tobacco (Nicotiana tabacum) in Virginia
Article first published online: 2 NOV 2010
© 2010 The Authors. Plant Pathology © 2010 BSPP
Volume 59, Issue 6, page 1164, December 2010
How to Cite
Parkunan, V., Johnson, C. S., Bowman, B. C. and Hong, C. X. (2010), First report of Phytophthora inundata associated with a latent infection of tobacco (Nicotiana tabacum) in Virginia. Plant Pathology, 59: 1164. doi: 10.1111/j.1365-3059.2010.02298.x
- Issue published online: 2 NOV 2010
- Article first published online: 2 NOV 2010
- Accepted 16 February 2010 at http://www.bspp.org.uk/ndr where figures relating to this paper can be viewed.
During a state-wide tobacco black shank survey in the summers of 2007 and 2009, four isolates were recovered (two each from stem pith and rhizosphere soil, respectively), that had a DNA fingerprint typical of Phytophthora inundata (Gallegly & Hong, 2008). These isolates were from a field producing flue-cured tobacco (cvs K326 and NC71, respectively) in Nottoway County with approximately 50–75% incidence of plants showing typical symptoms of black shank. All isolates produced non-papillate, ovoid to obpyriform sporangia, averaging 51 × 36 μm, through internal proliferation. Isolates formed hyphal swellings but failed to produce oospores with A1 and A2 mating type testers. These morphological characters and the complete ribosomal DNA internal transcribed spacer sequences (GenBank Accession No. FJ959406) confirmed their identity as P. inundata. These isolates were tested against three tobacco entries (Hicks, L8 and NC1071), generally used to differentiate P. nicotianae races. Multi-cell trays with five plants of each entry were challenged with 3 × 104 zoospores per plant and maintained under greenhouse conditions for four weeks along with control plants. The test was repeated twice. No disease symptoms were observed on any plants after four weeks. Symptomless root, stem and leaf tissue from inoculated and control plants were transferred separately to Phytophthora selective medium (PARPH-V8) after surface sterilization with 0·5% sodium hypochlorite and 70% ethanol. Phytophthora inundata was re-isolated from all inoculated plant samples, indicating that successful colonization occurred, as determined by direct colony-PCR single strand conformation polymorphism (Kong et al., 2005).
Phytophthora inundata was reported as a pathogen of shrubs and trees in Europe and South America (Brasier et al., 2003) and isolated from alfalfa roots in California (Ho et al., 2006). This pathogen was also documented to cause latent infection of Viburnum in Australia (Cunnington et al., 2006). This is the first report of a latent infection of tobacco by P. inundata. Investigations into this infection mechanism and its interactions with other pathogens are warranted to elucidate the role of P. inundata in tobacco fields.
The authors thank Altria Client Services and Philip Morris International for their funding of this research.
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