Systemic Aquired Resistances: Huanglongbing (HLB)
Huanglongbing (HLB), also known as Citrus Greening disease because fruit remain
green at stylar end after ripening (Bove, 2006).
The pathogen (Liberibacter asiaticus (Las), Liberibacter africanus
(Laf), and Liberibacter americanus (Lam)) is a Gram negative, unculturable,
phloem-limited bacterium (Doddapaneni et al., 2008).
Bacteria that cause HLB probably originated in China in the early 1900s (Bove, 2006).
HLB first detected in Florida in 2005 and by 2010 it had been identified in most
of the citrus growing counties in Florida. in the state. HLB now become a potential
threat to the entire U.S. citrus industry (Bove, 2006).
Disease Spread and Symptoms
The bacteria is transmitted to plants by Asian citrus psyllid (Diaphorina citri)
and psyllids can acquire liberibacter at an adult and third to fifth instar nymph
stage (da Graca, 2008).
The characteristic symptom includes yellow shoot with mottled leaves. Leaves are
thicker with corky veins (da Graca, 2008).
Fruit are lop-sided often green at the stylar end, contain aborted seed, discolored
vascular bundles, and have a bitter taste (da Graca, 2008).
Excessive defoliation and fruit drop (da Graca, 2008).
- Renovation of green house for conducting studies
- Purchase of disease free citrus plants
- Bove, J. M. 2006. Huanglongbing: A destructive, newly-emerging, centaury-old disease
of citrus. Journal of Plant pathology, 88: 7-37.
- Doddapaneni et al., 2008. Comparative phylogenomics and multigene cluster analyses
of the citrus huanglongbing associated bacterium Candidatus liberibacter.
BMC Research Notes, I:72: 1-9.
- De Graca, 2008. Biology, history and world status of Huanglongbing. Taller Internacional
sobre Huanglongbing de los citricos (Candidatus liberibactor spp) y el psilido
asiatico de los citricos (Diphornia citri). Hermosillo, Sonora, Mexico. pp
- Durrant and Dong, 2004. Systemic acquired resistance Annual Review of Phytopathology,
42: 185-209. Physiol. Mol. Plant Pathol. 71: 240-250.