Nymphs of the pomelo psyllid, Cacopsylla (Psylla) citrisuga Yang & Li, were collected from huanglongbing (HLB) symptomatic lemon trees, Citrus limon (L.) in Yunnan Province, China. DNA samples extracted from groups of 2–10 pomelo psyllid nymphs of all stages and from leaves of lemon plants were analyzed with nested-PCR in order to detect ‘Candidatus Liberibacter asiaticus’ (Las). The results showed that 24 out of the 49 lemon trees were Las-positive. Also psyllid nymphs collected from 10 out of the 24 Las-positive plants were Las-positive. DNA extracted from individual late stage nymphs (3rd to 5th instars) collected from Las-infected trees were then subjected to nested-PCR trials. Twelve out of the 29 nymphs proved to be Las positive. All nymphs collected from Las-negative lemon trees were also Las-negative. Most psyllid samples which showed positive in nested-PCR were also positive in conventional-PCR detection. The amplified fragment of the 16S rRNA gene of ‘Ca. Liberibacter spp.’ from positiv... RESUMEN Ninfas del psílido del pomelo, Cacopsylla (Psylla) citrisuga Yang & Li, fueron colectadas de árboles de limón, Citrus limon (L.), con síntomas de huanglongbing (HLB) en la provincia de Yunnan, China. Muestras de ADN extraídas de grupos de 2–10 ninfas de todos los estadios del psílido, y de hojas de limonero, fueron analizadas mediante PCR- anidada para detectar a ‘Candidatus Liberibacter asiaticus’ (Las). Los resultados mostraron que 24 de los 59 árboles fueron Las-positivo. Ninfas provenientes de 10 de los 24 árboles Las-positivos, también fueron Las-positivas. ADN extraído individualmente de ninfas de últimos estadios (3er a 5to instar) colectadas de arboles infectados con Las fueron sujetas a ensayos de PCR anidada. Doce de las veintinueve ninfas demostraron ser Las-positivas. Todas las ninfas colectadas de árboles de limon Las-negativos también fueron Las-negativas. La mayoría de muestras de psílidos que resultaron Las-positivas mediante el PCR anidado también fueron positivas en la detección ...

Citrus tristeza virus (CTV) is one of the most important citrus tree viruses: a graft-transmissible virus that can be vectored by several aphid species. Diaphorina citri is the insect vector of “Candidatus Liberibacter spp.”, a bacterium associated with citrus Huanglongbing (HLB). However, no detailed description of the relationship between CTV and D. citri has been reported. In this study, D. citri adults collected from CTV-infected “Shatangju” mandarin, “Newhall” sweet orange, and “fingered citron” trees in different orchards yielded CTV-positive rates of 40%, 65%, and 95%, respectively, upon detection by conventional PCR. Illumina HiSeq sequencing followed by de novo assembly recovered the primary full CTV genome from the RNA of 30 D. citri adults sampled from CTV-positive citrus plants. Molting and adult emergence did not affect the presence or titers of CTV within the D. citri; however, the persistence of CTV in psyllids varied among different host plant species. Groups of 10 D. citri (from a population 85% CTV-positive) were shown to potentially transmit CTV to two citrus species, “Shatangju” mandarin and “Eureka” lemon, yielding 58.33% and 83.33% CTV-positive plants, respectively. No transmission of CTV to orange jasmine plants occurred. Thus, this study reports on the ability of D. citri to acquire and transmit CTV, making D. citri as a vector of two important citrus pathogens, warranting further attention and investigation.