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United States Department of Agriculture

Agricultural Research Service

Research Project: IDENTIFICATION, CHARACTERIZATION, AND DETECTION OF FOREIGN AND NEWLY EMERGING DOMESTIC BACTERIA

Location: Foreign Disease-Weed Science

Title: First report of citrus canker caused by Xanthomonas citri in Somalia

Authors
item Balestra, G - UNIV DELLA TUSCIA, ITALY
item Sechler, Aaron
item Schuenzel, Erin
item Schaad, Norman

Submitted to: Plant Disease
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: March 1, 2008
Publication Date: June 1, 2008
Citation: Balestra, G.M., Sechler, A.J., Schuenzel, E., Schaad, N.W. 2008. First report of citrus canker caused by Xanthomonas citri in Somalia. Plant Disease. 92:981.

Interpretive Summary: Xanthomonas citri, the causal agent of citrus canker, has been reported in several countries in Africa, but not Somalia. During 2006 and 2007, erumpent lesions typical of citrus canker were observed on 8-10 year-old grapefruit trees in southern Somalia. Leaf samples diagnosed presumptively as citrus canker were mailed to the USDA-ARS Foreign Disease-Weed Science Research Unit (FDWSRU) at Ft. Detrick. To confirm identification of X. citri, isolations were made from several lesions and resulting xanthomonad-like mucoid, convex, colonies were purified and stored on agar slants. For pathogenicity tests, cultures were grown overnight in a liquid medium were used to inoculate leaves of lime seedlings. Symptoms were recorded after 30 days in a lighted dew chamber. Cultures S3 and S4 resulted in typical erumpent lesions. Isolations onto YDC agar resulted in mucoid, convex, yellow colonies typical of X. citri. This is the first report of X. citri on citrus plants in Somalia. Strains S3 and S4 have been deposited in International Collection of Phytopathogenic Bacteria (ICPB) at the FDWSRU, Ft. Detrick, MD, as ICPB 11650 and 11651, respectively.

Technical Abstract: Xanthomonas citri, causal agent of citrus canker, has been reported in several countries in Africa, but not Somalia. During 2006 and 2007, hyperplasia-type lesions, often surrounded by a water-soaked margin and yellow halo, typical of citrus canker caused by X. citri, were found on 8-10 year-old grapefruit (Citrus x paradisi Macfed) trees in southern Somalia. Leaf samples diagnosed presumptively as citrus canker using Xac ImmunoStrip® test kits were mailed to Ft. Detrick. To confirm identification of X. citri, isolations were made from several lesions from each sample onto YDC agar. Yellow xanthomonad-like mucoid, convex, colonies were purified and stored on YDC slants. Several cultures were grown overnight in liquid medium for pathogenicity tests using leaves of lime seedlings. Symptoms were recorded after 30 days in a lighted dew chamber at 30 degrees C/23 degrees C day/night. Cultures 3 and 4 produced erumpent lesions on lime and isolations onto YDC agar resulted in typical mucoid, convex, yellow colonies. This is the first report of X. citri on citrus plants in Somalia. Strains S3 and S4 have been deposited in International Collection of Phytopathogenic Bacteria at Ft. Detrick, MD as ICPB 11650 and 11651, respectively.

Last Modified: 8/21/2014
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