Poster Session: New and Emerging Diseases-Bacteria
First report of citrus huanglongbing in Texas.
M. KUNTA (1), M. Sétamou (2), M. Skaria (2), J. E. Rascoe (3), W. Li (3), M. K. Nakhla (3), J. V. da Graça (2)
(1) Texas A&M University-Kingsville, Weslaco, TX, U.S.A.; (2) Texas A&M University, Kingsville Citrus Center, Weslaco, TX, U.S.A.; (3) USDA APHIS, Beltsville, MD, U.S.A.
Huanglongbing (HLB), also known as citrus greening, is a destructive citrus disease associated with three alpha-proteobacteria species of ‘Candidatus Liberibacter’. The first report of HLB in the USA was from Florida in 2005 and ‘Ca. L. asiaticus’ (CLas) is the only species currently found in USA. On January 13, 2012, a Valencia sweet orange leaf sample from a commercial orchard in San Juan, TX gave a quantitative real-time PCR (qPCR) threshold cycle value of 23.41 and a positive PCR amplification product in conventional PCR (cPCR) using primers based on 16S rRNA and beta-operon genes. The cPCR products were sequenced and were 100% homologous to ‘Ca. L. asiaticus’. The sample tested negative for ‘Ca. L. americanus’ and ‘Ca. L. africanus’. Leaf blotchy mottle, twig die-back, yellow shoot, veinal chlorosis, lopsided and greening fruits were observed on CLas-positive trees, which immediately triggered an intensive survey of the disease in the area. CLas has only been detected in 25 Valencia trees (1%) and 10 Rio Red grapefruit trees (0.5%) in two adjacent orchards located on either side of a paved road, in the 2 months post initial disease confirmation. Infected trees have been removed and intensive psyllid control and surveys are continuing.
© 2012 by The American
Phytopathological Society. All rights reserved.