Mystery unraveled: Citrus Greening Causal Organism, Candidatus Liberibacter asiaticus Detected in Bangladeshi Sweet Orange

Citrus greening (huanglongbing; HLB) is considered as one of the most devastating citrus diseases in the world. It is caused by gram negative fastidious unculturable bacteria of Candidatus Liberibacter spp. Its Asian form Ca. L. asiaticus is the most destructive and widespread in Asia as well as in the Western hemisphere. Symptoms include yellowing of leaves with blotchy mottling that is not uniform across the leaf, small upright leaves with thickened leaf midribs and veins. It is often confused with nutrient deficiencies (e.g. zinc, manganese, magnesium, iron or boron deficiency symptoms) which causing substantial economic losses in many parts of Asia and Africa.To unravel the fact, a polymerase chain reaction (PCR) with specific primers A2/J5 was performed with genomic DNA extracted from midribs and petioles of symptomatic leaf samples. After gel electrophoresis a band of 703 bp was observed which is specific to Ca. L. asiaticus. The sequence data of ribosomal protein genes of the rplKAJL-rpoBC operon showed 99% identity with other isolates of Ca. L. asiaticus available in NCBI Genbank. Phylogenetic tree showed close relationship with Asian origin. These results confirmed the presence of Ca. L. asiaticus associated with citrus greening in Bangladesh.