Molecular Test to Assign Individuals within the Cacopsylla pruni Complex

Abstract

Crop protection requires the accurate identification of disease vectors, a task that can be made difficult when these vectors encompass cryptic species. Here we developed a rapid molecular diagnostic test to identify individuals of Cacopsylla pruni (Scopoli, 1763) (Hemiptera: Psyllidae), the main vector of the European stone fruit yellows phytoplasma. This psyllid encompasses two highly divergent genetic groups that are morphologically similar and that are characterized by genotyping several microsatellite markers, a costly and time-consuming protocol. With the aim of developing species-specific PCR primers, we sequenced the Internal Transcribed Spacer 2 (ITS2) on a collection of C . pruni samples from France and other European countries. ITS2 sequences showed that the two genetic groups represent two highly divergent clades. This enabled us to develop specific primers for the assignment of individuals to either genetic group in a single PCR, based on ITS2 amplicon size. All previously assigned individuals yielded bands of expected sizes, and the PCR proved efficient on a larger sample of 799 individuals. Because none appeared heterozygous at the ITS2 locus (i.e., none produced two bands), we inferred that the genetic groups of C . pruni , whose distribution is partly sympatric, constitute biological species that have not exchanged genes for an extended period of time. Other psyllid species (Cacopsylla, Psylla, Triozidae and Aphalaridae) failed to yield any amplicon. These primers are therefore unlikely to produce false positives and allow rapid assignment of C . pruni individuals to either cryptic species.

Multi-scale spatial genetic structure of a vector-borne plant pathogen in orchards and wild habitat

“…The psyllid vector C. pruni is known to present two cryptic species currently called A and B, which show clear genetic differences despite being ecologically and morphologically indistinguishable 37,38 . All the collected psyllids were successfully assigned to either species.…”

Potential Psyllid Vectors of Candidatus Phytoplasma Mali and Candidatus Phytoplasma Pyri in Turkey

“…Finally we gave up differentiating the two species and denoted them as the C. melanoneura-C. affinis complex. PCR and RFLP analysis of phytoplasma from individual psyllids: Total DNAs were extracted from whole psyllids individually using the High-Salt method based on TNES (10 mM Tris, pH 7.5, 400 mM NaCl, 100 mM EDTA, 0.6 % SDS) buffer in semi-deep well plates (Peccoud et al, 2013). DNA was diluted in 60 μL of sterile water and stocked at -20°C before to be used for phytoplasma detection by PCR analysis.…”

A framework for estimating the effects of sequential reproductive barriers: Implementation using Bayesian models with field data from cryptic species

“…Our model system, Cacopsylla pruni Scopoli (Sternorrhyncha: Psyllidae), includes two unnamed cryptic species that are strongly genetically divergent but have yet to show ecological or morphological differences (Sauvion et al 2007;Peccoud et al 2013). These species co-occur at several sites in Southern France (Sauvion et al 2007) on shrubs of genus Prunus, on which the insects feed, reproduce, and die in spring ( Fig.…”

“…This predominance does not indicate that postinsemination barriers contributed little to the divergence of A and B species. These barriers may have reinforced premating isolation [see Servedio and Noor (2003); Coyne and Orr (2004) for a review on reinforcement] and have certainly permitted genetic divergence between C. pruni species (Sauvion et al 2007;Peccoud et al 2013) in the face of cross-insemination. Some barriers (RI prog , Fig.…”