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Poster: Diseases of Plants: Disease Detection & Diagnosis


Occurrence of a Citrus canker strain of limited host specificity in Texas
M. KUNTA (1), J. da Graça (1), B. Salas (2), D. Bartels (2), J. Park (1), G. Santillana (3), V. Mavrodieva (3) (1) Texas A&M University-Kingsville Citrus Center, U.S.A.; (2) USDA APHIS PPQ CPHST Mission Laboratory, U.S.A.; (3) CPHST Beltsville Laboratory

In October 2015, a Mexican lime exhibiting citrus canker-like symptoms was found by the USDA-APHIS-PPQ citrus disease survey in a residential property in Cameron County, Texas. The Texas A&M University-Kingsville Citrus Center detected citrus canker using a real-time PCR analysis. The USDA-APHIS-PPQ Lab in Beltsville, MD confirmed that it was a Xanthomonas citri subsp. citri isolate. A delimiting survey was initiated by USDA and by February 2016, 169 suspect leaf samples were sent to the PPQ Beltsville lab for analysis. Of 118 samples positive for citrus canker, all within a 5-mile radius, 116 were from Mexican lime, 1 was from Kaffir lime and 1 from Ponderosa lemon. Survey data collected on stem lesions suggested the oldest lesions to be between 4 – 6 years old. To examine the host range of the TX citrus canker strain, four pots each of 11 different citrus varieties, including the major commercial varieties grown in TX, were inoculated by syringe infiltration of symptomatic crude leaf extracts. The only citrus plants that developed clear canker lesions were Mexican limes. A combination of serological and molecular tests also suggested that the Texas citrus canker isolate was different from the typical Asiatic strain (Xac A) and more similar to other known X. citri subsp. citri strains with limited host range such as Xac AW or A*. Xac AW strain was previously reported from Florida on Mexican lime and Alemow, a close relative of Kaffir lime.