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First Report of Phakopsora pachyrhizi Telia on Kudzu in the United
States. C. L. Harmon, Southern Plant Diagnostic Network and Department of
Plant Pathology, University of Florida, Gainesville; P. F. Harmon, Department of
Plant Pathology, University of Florida, Gainesville; T. A. Mueller, Department
of Crop Science, University of Illinois;
J. J. Marois, Department of Plant Pathology, North Florida Research and
Education Center, University of Florida, Quincy; and G. L. Hartman, USDA-ARS and
Department of Crop Science, University of Illinois, Urbana. Plant Dis. 90:380,
2006; published on-line as DOI: 10.1094/PD-90-0380C. Accepted for publication 19
December 2005.
Soybean rust caused by Phakopsora pachyrhizi H. Sydow & Sydow was
first reported in the continental United States during 2004 (2). By 10 November
2005, the disease was confirmed in eight southern states (Florida, Georgia,
Alabama, Mississippi, South Carolina, North Carolina, Louisiana, and Texas).
Diagnoses have been based on visual observation of uredinia and urediniospores
of the pathogen followed by polymerase chain reaction confirmation. On 10
November 2005, uredinia and telia were identified on leaves of kudzu (Pueraria
lobata) in central Florida. Telia first were noted as dark brown-to-black
flecks on the abaxial leaf surface intermingled with abundant tan-to-light brown
uredinia. Of 200 leaves examined, 143 (72%) had telia. The number of telia
ranged from a few (1/cm(^2)) that were scattered to many (73/cm(^2)). Telia were
approximately the same diameter as uredinia, but were appressed to the leaf
surface and pigmented. Twenty telia were excised from host tissue with the aid
of a dissecting microscope and a 20 gauge hypodermic needle. Telia averaged 89 ×
100 µm (n = 20, σ = 17 and 16 µm, respectively). Four telia were crushed
and five teliospores from each averaged 4.3 × 8.3 µm (n = 20, σ = 0.5 and
0.9 µm, respectively). Pale yellowish brown-to-hyaline teliospores were similar
in color to urediniospores. Observations matched descriptions by Ono et al. (1).
To our knowledge, this is the first report of the telial stage of P.
pachyrhizi in the United States.
References: (1) Y. Ono et al. Mycol. Res. 96:825, 1992. (2) R. W.
Schneider et al. Plant Dis. 89:774, 2005.
Digital image of telia, uredinia, and urediniospores
of Phakopsora pachyrhizi on a kudzu leaf exhibiting
symptoms
of Asian soybean rust (100X).
Digital image of a thin section through a kudzu leaf
and a
telium
of Phakopsora pachyrhizi (dark field objective at 400X).
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