Transmission rates of ‘Candidatus Liberibacter asiaticus’ to greenhouse seedlings by laboratory colonies of Asian citrus psyllid (Hemiptera: Liviidae)

Authors: Hall, David; Moulton, Kathryn

Submitted to: Journal of Economic Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/20/2018
Publication Date: 8/14/2018
Citation: Hall, D.G., Moulton, K.M. 2018. Transmission rates of ‘Candidatus Liberibacter asiaticus’ to greenhouse seedlings by laboratory colonies of Asian citrus psyllid (Hemiptera: Liviidae). Journal of Economic Entomology. https://doi.org/10.1093/jee/toy240.
DOI: https://doi.org/10.1093/jee/toy240

Interpretive Summary: Citrus greening is a serious disease caused by a bacterium transmitted by the Asian citrus psyllid. Plant resistance holds promise as a disease-management strategy, thus breeders are developing new varieties and evaluating these for disease resistance. An inoculation procedure using psyllids infected by the bacterium was established to expedite evaluations. The procedure provides a 77% average (range 40 to 100%) success rate in infecting seedlings. Transmission rates were positively correlated with the percentage of psyllids that tested positive for the bacterium.

Technical Abstract: Asiatic huanglongbing (HLB), also known as citrus greening or yellow shoot disease, is a serious disease putatively caused by the bacterium ‘Candidatus Liberibacter asiaticus’ (CLas) transmitted by the Asian citrus psyllid (ACP) (Diaphorina citri Kuwayama). Plant resistance to CLas holds promise as a strategy for reducing the economic impact of HLB, thus citrus breeders are developing new varieties and cultivars and evaluating these for resistance/tolerance to CLas. A high-throughput inoculation program was established to expedite inoculating germplasm. Colonies of ACP maintained on CLas-infected plants are used for the inoculations. The primary inoculation step is to cage a healthy citrus seedling with flush (new leaf growth) for a two-week infestation of 20 adult ACP from these colonies. The objective of research presented here was to evaluate inoculation rates under this procedure. Ten sets of 20 healthy citrus seedlings were subjected to the procedure, one set a month, and the percentage of seedlings successfully inoculated based on quantitative polymerase chain reaction (qPCR) was determined six months after each two-week infestation. The results indicated a 77% mean transmission rate (success rate in infecting seedlings), with rates ranging from 40 to 100%. Transmission rates were positively correlated with the percentage of ACP that tested positive for CLas.