Researchers found evidence that Huanglongbing, also known as citrus greening, is an immune-mediated disease that might be mitigated with antioxidants and the growth hormone gibberellin, shedding light on the mechanism that causes this disease. The associated paper was recently published in Nature Communications.
Huanglongbing, which affects citrus trees and ornamental plants, is caused by the bacterium Candidatus liberibacter spp., transmitted by the citrus psyllid, a biting-sucking insect vector which also causes considerable direct damage to hosts. The African citrus psyllid (Trioza erytreae), vector of Candidatus liberibacter africanus, is listed as a quarantine pest in Europe and its presence in Portugal has been expanding. Citrus greening is considered the most serious disease worldwide for citrus and ornamental plants.
The team from the Citrus Research and Education Center at the University of Florida (USA) shows that the infection of sweet orange trees (Citrus sinensis) by the bacterium Candidatus liberibacter asiaticus induces a systemic chronic immune response in the plant’s phloem tissue, mimicking systemic chronic inflammation diseases of humans, leading to cell death within the phloem tissue.
The conclusion that this is an immune-mediated pathology “helps guide the battle against this notorious disease”, state the authors in the referred paper. The researchers deem it likely that horticultural approaches that suppress the oxidative stress of citrus greeing-infected plants can alleviate the damage, including optimized usage of plant growth hormones such as gibberellin and brassinosteroids, and also antioxidant treatments.
Highlighted image © UF/IFAS Citrus Research and Education Center