October 4, 2005
From: American Phytopathological Society, Plant Disease Notes [edited] <http://www.apsnet.org/pd/searchnotes/2005/PD-89-1132B.asp>

Morphologic and pathometric characterization of the Asian soybean rust (Phakopsora pachyrhizi) on Kudzu (Pueraria lobata) in Argentina
M. A. Carmona, Facultad de Agronomia, Universidad de Buenos Aires, Av. San Martin 4453 (1417), Buenos Aires, Argentina; C. Fortugno, INTA (retired) CC 25 (1712) Castelar, Buenos Aires, Argentina; and P. L. Achaval, Facultad de Agronomia, Universidad de Buenos Aires, Av. San Martin 4453 (1417), Buenos Aires, Argentina Plant Dis. 89:1132, 2005; published on-line as DOI: 10.1094/PD-89-1132B. Accepted for publication 14 Jul 2005.

Asian soybean rust (ASR) is a very important disease caused by _Phakopsora pachyrhizi_. The disease has emerged as a major threat to soybean production in South America since 2001. During the 2003-2004 growing season, _P. pachyrhizi_ spread rapidly throughout most soybean-growing areas of northwestern and northeastern Argentina (1).

One widespread naturalized host in the northeastern part of the country is kudzu (_Pueraria lobata_). Plants of severely infected kudzu were sampled during January 2005 in Cerro Azul (29o 29' S Misiones Province) to quantify _P. pachyrhizi_ infection and morphologically characterize the fungus in leaves. The number of lesions, uredinia per square cm, and uredinia per lesion were recorded from the undersides of 50 leaflets that were visually showing rust symptoms.

The average number of lesions and uredinia per square cm was 14 (4 to 22), and 24 (5 to 78), respectively. The number of uredinia per lesion was 3 (one to 10). 20 leaflets from the lower canopy averaged
55 (42 to 78) uredinia per square cm. The average size of urediniospores was 18.4 micrometers wide (12.5 to 22.5) and 22.7 micrometers long (17.5 to 26.3). Although important epidemics of ASR have not been registered on soybean crops in January (2) because of adverse conditions, the fungus was observed on kudzu plants.

To our knowledge, this is the 1st report of morphologic and pathometric characterization of _P. pachyrhizi_ on kudzu in Argentina.

References: (1) M. A. Carmona et al Plant Dis. 89:109, 2005. (2) SINAVIMO, Sistema Nacional Argentino de Vigilancia y Monitoreo de plagas. Roya de la soja: Resultados de la campana 2004-2005. On-line publication. SENASA, 2005.

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ProMED-mail
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[This information on the morphologic and pathometric characteristics of ASR will be useful in determining the significance of lesion numbers and densities of ASR spores on kudzu under various climatic conditions. For a comprehensive review of kudzu and its management, see the following links:
<http://www.pfmt.org/standman/kudzu.htm>
<http://www.invasive.org/eastern/biocontrol/pdf/25Kudzu.pdf>
- Mod.DH]

[For images of rampant kudzu, try googling "kudzu" under images, e.g.
<http://dnr.metrokc.gov/wlr/lands/weeds/photos/kudzu_impact.jpg>. 
- Mod.JW]

[see also in the archive:
Soybean rust, Asian strain - USA (FL): 1st report 2005 20050309.0693
Soybean rust, Asian strain - USA (GA) 20050429.1196
Soybean rust, Asian strain - Americas: alert 20050528.1476
Soybean rust, Asian strain - USA (GA) 20050505.1245
Soybean rust, Asian strain - USA (LA) 20050624.1769
Soybean rust, Asian strain - USA (FL) (02) 20050620.1731
Asian soybean rust, Asian strain - USA (multistate) 20050724.2133
Soybean rust, Asian strain - USA (AL) 20050715.2029
Soybean rust, Asian strain - USA (multistate)(03) 20050714.2005
Soybean rust, Asian strain - USA (multistate)(02): Florida 20050708.1938
Soybean rust, Asian strain - USA (multistate) 20050702.1868
Soybean rust, Asian strain - USA (multistate)(04) 20050829.2556
Soybean rust, Asian strain - USA (GA)(03) 20050827.2531
Soybean rust, Asian strain - USA (AL)(03) 20050826.2528
Soybean rust, Asian strain - USA (AL)(02) 20050824.2496
Soybean rust, Asian strain - USA (SC) 20050818.2414
Soybean rust, Asian strain - USA (FL)(03) 20050815.2386
Soybean rust, Asian strain - USA (Multistate)(06) 20050808.2318
Soybean rust, Asian strain - USA (multistate)(05): susp. 20050806.2291
Soybean rust - USA (multistate)(04) 20050806.2289
Soybean rust, Asian strain - USA (multistate) (07) 20050909.2672
Soybean rust, Asian strain - USA (GA) (04) 20050905.2623]