A New Aculodes Species (Prostigmata: Eriophyidae) Described from an Invasive Weed by Morphological, Morphometric and DNA Barcode Analyses †

A new species of eriophyoid mite, Aculodes marcelli sp. nov., was discovered on cheatgrass, Anisantha tectorum (L.) Nevski (syn. Bromus tectorum L.), an annual grass that is native to Eurasia and Northern Africa. This grass was introduced to North America near the end of the 19th century and now is widespread and associated with the observed increases in the size, frequency, and intensity of wildfires in western N. America. In this paper, A. marcelli sp. nov., is morphologically described and illustrated. Compared with other Aculodes spp., it differs based on morphology and the sequence of the mitochondrial cytochrome oxidase gene, subunit I (MT-CO1). Results of morphometric analysis showed clear differentiation between A. marcelli sp. nov., and the most similar congener, A. altamurgiensis from Taeniatherum caput-medusae. Analysis of MT-CO1 sequence divergence revealed significant levels of genetic variation (17.7%) and supported the results from the morphometric analysis; therefore, it is determined that they are two different species. Aculodes marcelli sp. nov., is a new candidate agent for classical biological control of A. tectorum. © 2022 by the authors

Identification and ecology of alternative insect vectors of ‘Candidatus Phytoplasma solani’ to grapevine

Bois noir, a disease of the grapevine yellows complex, is associated with 'Candidatus Phytoplasma solani' and transmitted to grapevines in open fields by the cixiids Hyalesthes obsoletus and Reptalus panzeri. In vine-growing areas where the population density of these vectors is low within the vineyard, the occurrence of bois noir implies the existence of alternative vectors. The aim of this study was to identify alternative vectors through screening of the Auchenorrhyncha community, phytoplasma typing by stamp gene sequence analyses, and transmission trials. During field activities, conducted in Northern Italy in a vineyard where the bois noir incidence was extremely high, nine potential alternative insect vectors were identified according to high abundance in the vineyard agro-ecosystem, high infection rate, and harbouring phytoplasma strains characterized by stamp gene sequence variants found also in symptomatic grapevines. Transmission trials coupled with molecular analyses showed that at least eight species (Aphrodes makarovi, Dicranotropis hamata, Dictyophara europaea, Euscelis incisus, Euscelidius variegatus, Laodelphax striatella, Philaenus spumarius, and Psammotettix alienus/confinis) are alternative vectors of 'Candidatus Phytoplasma solani' to grapevines. These novel findings highlight that bois noir epidemiology in vineyard agro-ecosystems is more complex than previously known, opening up new perspectives in the disease management

New strain of 'Candidatus Phytoplasma ulmi' infecting Ulmus minor and U. laevis in Serbia

Elm yellows (EY) phytoplasma (‘Candidatus Phytoplasma ulmi’) is the causal agent of a decline in American elms in North America, and in Eurasian elm species and hybrids in Europe (Lee et al., 2004). EY is known to infect different Ulmus species: U. americana, U. minor, U. rubra, U. alata, U. serotina, U. crassifolia and U. chenmoui, showing different symptoms such as stunting, witches’ broom, yellowing and general decline of the plants (Marcone et al., 1997; Griffiths et al., 1999). In September 2007 leaves with petioles from eighteen elm trees showing symptoms of discrete leaf yellowing were collected from three different sites in northeast Serbia near the villages of Srednjevo, Ljubicevo and TuvajiÇ. From each site six samples were collected. At two sites (Srednjevo and Ljubicevo) the affected plants were of European field elm (U. minor), and at the third site they were of European white elm (U. laevis). Leaves of six symptomless young elm trees (U. minor) collected near Belgrade served as the controls. Total nucleic acids were extracted from fresh leaf midribs and petioles using the CTAB method (Angelini et al., 2001). Phytoplasma identification was conducted using a nested PCR assay with P1/P7 and F2n/R2 primers on the 16S rRNA gene, followed by RFLP analysis with MseI restriction enzyme. Positive results were obtained in nine affected U. minor samples and five U. laevis samples, with RFLP profiles indicating the presence of phytoplasmas of the 16SrV group. None of the symptomless plants were positive for the presence of phytoplasma. Further characterization was performed by amplifying the ribosomal protein genes l22 and s3 using primers rp(V)F1/rpR1 followed by rp(V)F1A/rp(V)R1A, finally by digestion with MseI and Tsp509I (Lee et al., 2004). RFLP profiles with MseI enzyme showed the presence of EY phytoplasmas of 16SrV-A group, but profiles obtained with Tsp509I enzyme were different from the EY control sample and were more similar to FD-C (16Sr V-C group). Subsequently two of these products, one from U. minor and one from U. laevis, were sequenced (GenBank Acc. No. EU592500, EU592501) and showed identical nucleotide sequence to each other. blast analyses showed 99% similarity of these isolates with reference strain EY1T (AY197675). Nucleotide changes are located in two out of three unique regions of the rpl22–rps3 genes reported by Lee et al. (2004) as being species specific for ‘Candidatus Phytoplasma ulmi’. This is the first report of elm yellows phytoplasma belonging to rRNA group 16SrV-A infecting elm species in Serbia and of its association with U. laevis. It is also the first evidence of strain differences in ‘Candidatus Phytoplasma ulmi’ detectable by RFLP analysis of ribosomal protein gene PCR products