Plant Disease (2018) 102, 1108-1114

Courtney A. Gallup, Kestrel L. McCorkle, Kelly L. Ivors and David Shew (2018)
Characterization of the black shank pathogen, Phytophthora nicotianae, across North Carolina tobacco production areas
Plant Disease 102 (6), 1108-1114
Abstract: Black shank disease of tobacco, caused by the oomycete Phytophthora nicotianae, is a major threat to production in the United States and tobacco-producing areas worldwide. In a statewide survey of North Carolina, the rapid shift from race 0 to race 1 was documented. Collected pathogen isolates were characterized phenotypically for mating type and mefenoxam sensitivity, and genotypically by comparing sequences from three cytoplasmic and two nuclear regions. Both the A1 and A2 mating types were found throughout the state. When both mating types were recovered from the same field, pairings of isolates yielded viable oospores, indicating for the first time the potential for sexual sporulation by P. nicotianae in natural populations. Because the loss of complete resistance required a renewed use of the fungicide mefenoxam, a subset of the survey isolates was screened for sensitivity to the fungicide. All isolates were sensitive, with a mean effective concentration to inhibit 50% of hyphal growth of 0.4 μg/ml that was similar across mating types and races. Molecular characterization of 226 isolates revealed that the pathogen exists as multiple clonal types within the state. Genetic diversity among the pathogen population and the potential for sexual recombination may help explain the ability of the pathogen to rapidly adapt to host resistance genes.
(The abstract is excluded from the Creative Commons licence and has been copied with permission by the publisher.)
Link to article at publishers website
Database assignments for author(s): David Shew, Kestrel McCorkle, Courtney A. Gallup

Research topic(s) for pests/diseases/weeds:
surveys/sampling/distribution
pesticide resistance of pest

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Pest and/or beneficial records:

Beneficial	Pest/Disease/Weed	Crop/Product	Country	Quarant.
	Phytophthora nicotianae	Tobacco (Nicotiana tabacum)	U.S.A. (SE)