Molecular identification and characterization of citrus greening bacterium, Candidatus Liberibacter asiaticus associated with decline of Nagpur mandarin orange in Vidarbha region, Maharashtra.

摘要

Extensive surveys were undertaken across the Nagpur orange belt of Vidarbha, Maharashtra, India, during 2006-07. Young leaf and twig samples showing characteristic symptoms of citrus greening disease (CGD; caused by Candidatus Liberibacter asiaticus) in declining trees were collected from private Nagpur orange orchards situated at Katol, Kondhali and Kalmeshwar areas of Nagpur. The phylogenetic analysis revealed that the Nagpur CGD bacterium clustered together with the Candidatus Liberibacter asiaticus isolates. Candidatus Liberibacter africanus isolate and Candidatus Liberibacter americanus isolates formed a different cluster. The genetic distance from other members of alpha -Proteobacteria was even higher. Within the Candidatus Liberibacter asiaticus group, genetic distance of Nagpur isolate from the Poona strain was higher. Overall, PCR detection, sequencing and subsequent sequence analysis of 3 Nagpur CGD bacterium isolates indicated that all the isolates are the same and are closer to Candidatus Liberibacter asiaticus than Candidatus Liberibacter africanus or Candidatus Liberibacter americanus. The results also indicated that Candidatus Liberibacter asiaticus can induce chlorosis and decline symptoms on the mandarin tree.