Virus-Based RNAi Used to Control Huanglongbing

Virus-based vectors have been used as laboratory tools for short term experiments on herbaceous plants. They are stable enough to be used for introducing foreign genes to plants. However, the development of stable vectors has now showed potential use in perennial plants.

Citrus tristeza virus (CTV), a stable virus-based vector, is being considered for use in the control of Huanglongbing (HLB). Huanglongbing, also known as Citrus Greening disease, is caused by the bacteria Candidatus Liberibacter asiaticus (CLas). Although there are no known effective control for CLas, the CTV vector aims to control HLB by controlling its vector, the Asian citrus psyllid (Diaphorina citri). This insect targets the plants' phloem, which is also where both CLas and CTV thrive in the plant. This is exploited to develop a method to control HLB through RNA interference (RNAi).

CTV-RNAi vector with the abnormal wing disc (Awd) gene of D. citri, induces an altered Awd gene expression when ingested by the insects' nymphs. The altered expression silences the Awd gene which results in malformed-wing phenotype in adults and increased adult mortality. This impaired ability potentially limits the successful vectoring of CLas bacteria between citrus trees.