First report on molecular evidence of Candidatus Liberibacter asiaticus associated with citrus Huanglongbing in Venezuela

摘要

Huanglongbing disease (citrus greening; HLB) is currently the most economically damaging disease of citrus trees, and has been associated with the collapse of the several citrus industries in Asia and America. The disease is associated with the presence of a phloem restricted alpha proteobacteria species of the ‘Candidatus Liberibacter’ genus. ‘Candidatus Liberibacter asiaticus’ (CLas) is the dominant species found in South America (Lopes et al. 2009). In 2017, branches were collected from Citrus sp. trees showing mild to severe yellowing on the shoots, lopsided and greening fruits and tree decline in various regions in Venezuela. To verify the presence of CLas, total DNA was extracted from single leaf midribs and subjected to PCR amplification with primers sets OI1/OI2c targeting the 16S rDNA locus (Jagoueix et al. 1994) and A2/J5 targeting the beta-operon locus of ribosomal proteins (Hocquellet et al. 1999). A total of 87 out of 104 samples (83.7) tested positive with both primer sets.