| Huanglongbing is a devastating disease of citrus that has recently become established in Florida. In the United States Huanglongbing is caused by the uncultured Alphaproteobacteria, Liberibacter asiaticus (Las). Disease is thought to be caused when the bacteria colonize the plant's phloem where they multiply and block phloem sieve elements thereby depriving the plant tissues of nutrition eventually leading to death of the tree. Las is vectored by a Sternorrhynchian insect, the Asian citrus psyllid Diaphorina citri, which transmits it during feeding. Huanglongbing, or citrus greening, is killing mature trees and decreasing the quality of fruit to unmarketable levels greatly damaging Florida's 9 billion dollar citrus industry. Huanglongbing was first detected in Florida in 2005 and in the time since then no reliable treatment or resistant citrus strain has been developed. Work in this area has progress slowly and has been hindered in many respects by the lack of a pure axenic culture of the pathogen, the primary tool of bacterial plant pathology.;An in-depth functional comparison of the uncultured Liberibacter pathogens and their closest cultured relative L. crescens may hold the key to developing a sustained and vigorous culture for Liberibacter species. Physiological description, genome sequence, and gene expression data of L. crescens have contributed to this effort. Meanwhile, the development of L. crescens as a culturable model will hasten discovery and improve understanding of the disease. L. crescens was isolated from the phloem of a hybrid papaya and attempts are underway to reintroduce L. crescens into its natural host or other Liberibacter hosts such as citrus and potato. Accomplishing this would allow study of a Liberibacter species as it associates with its host as well as in vitro manipulation.;The discovery, description, and distribution of L. crescens is anticipated to aid in the advancement of Huanglongbing research. Investigators worldwide now have access to this invaluable proxy for the study of not only L. asiaticus but other uncultured Liberibacter pathogens such as L. solanacearum and L. africanus.. |
