Unsuitability of indigenous South American Rutaceae as potential hosts of Diaphorina citri.

BACKGROUND: 'Candidatus Liberibacter asiaticus' is transmitted by Diaphorina citri, an insect with a wide range of hosts in Rutaceae. Species related to Citrus occur in Brazilian forests where they may serve as hosts for psyllids and infested citrus orchards. RESULTS: The suitability of plants as hosts of D. citri was classified into four groups. Group I (high suitability): Citrus × aurantium 'Valencia', 'Citrus limonia', Murraya paniculata (syn. Murraya exotica L.) (Aurantioideae: Aurantieae) and Bergera koenigii (Aurantioideae: Clauseneae). Group II (intermediate to low suitability): Citrus (Poncirus) trifoliata 'Pomeroy', Citrus wintersii, Swinglea glutinosa (Aurantieae) and Clausena lansium (Clauseneae). Group III (not suitable): Aegle marmelos, Atalantia buxifolia, Citrus ('Microcitrus') sp. (Aurantieae) and Helietta apiculata (Amyridoideae). Group IV (non-hosts): Glycosmis pentaphylla (Clauseneae), Balfourodendron riedelianum, Casimiroa edulis, Esenbeckia febrifuga, Esenbeckia leiocarpa, Metrodorea stipularis, Zanthoxylum rhoifolium (Amyridoideae) and Dictyoloma vandellianum (Cneoroideae). Insects survived longer on newly differentiated leaves compared with fully expanded soft leaves. Psyllids either did not develop or did not survive for long on most Group IV species, all of which, with the exception of G. pentaphylla, occur naturally in Brazilian forests. CONCLUSION: Citrus relatives occurring in forests near citrus orchards are not suitable hosts of D. citri and, therefore, do not contribute to huanglongbing spread. © 2018 Society of Chemical Industry.

Phylogeography of Diaphorina citri (Hemiptera: Liviidae) and its primary endosymbiont, 'Candidatus Carsonella ruddii': an evolutionary approach to host-endosymbiont interaction.

BACKGROUND: In insects, little is known about the co-evolution between their primary endosymbionts and hosts at the intraspecific level. This study examined co-diversification between the notorious agricultural pest Diaphorina citri and its primary endosymbionts (P-endosymbiont), 'Candidatus Carsonella ruddii' at the population level. RESULTS: Maximum likelihood, haplotype network, principal components and Bayesian clustering identified three lineages for D. citri and its P-endosymbiont: a Western clade containing individuals from Pakistan, Bhutan (Phuentsholing), Vietnam (Son La), USA, Myanmar and China (Ruili, Yunnan); a Central clade, with accessions originating from Southwest China, Bhutan (Tsirang) and Bangladesh; and an Eastern clade containing individuals from Southeast Asia, and East and South China. A more diverse genetic structure was apparent in the host mitochondrial DNA than their P-endosymbionts; however, the two sets of data were strongly congruent. CONCLUSION: This study provides evidence for the co-diversification of D. citri and its P-endosymbiont during the migration from South Asia to East and Southeast Asia. We also suggest that the P-endosymbiont may facilitate investigations into the genealogy and migration history of the host. The biogeography of D. citri and its P-endosymbiont indicated that D. citri colonized and underwent a secondary dispersal from South Asia to East and Southeast Asia. © 2018 Society of Chemical Industry.