Cultivation of 'Candidatus Liberibacter asiaticus', 'Ca. L. africanus', and 'Ca. L. americanus' associated with huanglongbing.
A new medium designated Liber A has been designed and used to successfully cultivate all three 'Candidatus Liberibacter spp.,' the suspect causative agents of huanglongbing (HLB) in citrus. The medium containing citrus vein extract and a growth factor sustained growth of 'Ca. Liberibacter spp.' for four or five single-colony transfers before viability declined. Colonies, positive for 'Ca. L. asiaticus' by a 16s-based rDNA real-time polymerase chain reaction (RT-PCR) assay and sequencing, were irregular-shaped, convex, and 0.1 to 0.3 mm after 3 to 4 days. Suspect 'Ca. L. asiaticus' and 'Ca. L. americanus' cells were observed in infected tissue and on agar culture by scanning electron microscopy. The cells were ovoid to rod shaped, 0.3 to 0.4 by 0.5 to 2.0 microm, often with fimbriae-like appendages. Two strains of 'Ca. L. asiaticus' and one of 'Ca. L. americanus' grown on Liber A medium were pathogenic on citrus and could be isolated from noninoculated tissues of inoculated trees and seedlings 9 and 2 months later, respectively. The identity was confirmed by RT-PCR and 16s rDNA sequencing. This is the first report of the cultivation and pathogenicity of 'Ca. L. asiaticus' and 'Ca. L. americanus' associated with symptoms of HLB.
U.S. Department of Agriculture-Agricultural Research Service Foreign Disease Weed Science Research, Ft. Detrick, MD 21702, USA.
A
A
Sechler
E L
EL
Schuenzel
P
P
Cooke
S
S
Donnua
N
N
Thaveechai
E
E
Postnikova
A L
AL
Stone
W L
WL
Schneider
V D
VD
Damsteegt
N W
NW
Schaad
D002957:Citrus / Q000382:microbiology* / Q000648:ultrastructure; D003470:Culture Media / Q000737:chemistry / Q000494:pharmacology*; D046508:Culture Techniques; D010935:Plant Diseases / Q000382:microbiology*; D018515:Plant Leaves / Q000382:microbiology / Q000648:ultrastructure; D012336:RNA, Ribosomal, 16S / Q000235:genetics; D012230:Rhizobiaceae / Q000187:drug effects* / Q000254:growth & development* / Q000302:isolation & purification / Q000472:pathogenicity / Q000648:ultrastructure
D003470:Culture Media; D012336:RNA, Ribosomal, 16S