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Our previous studies reported that phytoplasma was the causative agent of the pine disease in the Curonian Spit, Lithuania. In this study, insects from diseased pine trees and their adjacent areas were collected from 2016 to 2019 to further identify potential insect vectors that spread phytoplasmas. A total of 1018 phloem-feeding insects (order Hemiptera) were identified, 98.62% of which were aphids (Aphididae), and no known phytoplasma vectors were found. The results from semi-nested polymerase chain reaction (PCR) using phytoplasma-specific universal primers revealed that phytoplasmas were detected in Scots pine aphids (Cinara pini (Linnaeus, 1758)), waxy grey pine needle aphids (Cinara pineti (Fabricius, 1781)), and species-unknown aphids. Further sequence analysis and virtual RFLP (restriction fragment length polymorphism) analysis of aphid-harbored phytoplasma strains indicated that they were closely related to 'Candidatus Phytoplasma pini' (16SrXXI-A), but mainly 16SrXXI-A variants, which were also main strains identified in diseased pine trees. In addition, three new phytoplasma subgroups were delineated in the present study. Subgroups 16SrXXI-C and 16SrXXI-D were unveiled from previously identified (but classification was overlooked) Lithuanian pine phytoplasma strains. Subgroup 16SrXXI-E was discovered from the newly identified aphid-harbored phytoplasmas. Further transmission trial studies on these aphids will provide insights into the epidemiology and pathosystem of pine phytoplasma diseases, as well as disease management. Key words: genetic diversity, insect transmissible plant pathogens, aphid. Nos etudes precedentes ont rapporte qu'un phytoplasme etait l'agent causal de la maladie du pin dans l'isthme de Courlande, en Lituanie. Dans cette etude, des insectes provenant de tiges de pin malades et des zones adjacentes ont ete recoltes de 2016 a 2019 afin de poursuivre l'identification des insectes vecteurs potentiels qui propagent les phytoplasmes. Au total, 1018 insectes piqueurs suceurs (ordre des Hemipteres) ont ete identifies; 98,62 % etant des pucerons (Aphididae), et aucun phytoplasme connu n'a ete observe. Les resultats de l'amplification en chaine par polymerase (ACP) a demi imbriquee en utilisant des amorces universelles pour phytoplasmes ont reveles que des phytoplasmes ont ete detectes chez des pucerons du pin sylvestre (Pinus sylvestris L.) (Cinara pini (Linnaeus, 1758)), le puceron des aiguilles du pin (Cinara pineti (Fabricius, 1781)) et des pucerons d'espece inconnue. D'autre analyses virtuelles de sequencage et de polymorphisme de la longueur des fragments de restriction (RFLP) des races de phytoplasmes transportes par des pucerons ont indique qu'ils etaient etroitement relies au 'Candidus Phytoplasma pini' (16SrXXI-A), mais surtout aux variants de 16SrXXI-A, qui etaient aussi les principales races identifiees chez les tiges de pin malades. De plus, trois nouveaux sous-groupes de phytoplasmes ont ete delimites dans cette etude. Les sous-groupes 16SrXXI-C et 16SrXXI-D ont ete devoiles a partir de races de phytoplasmes du pin de Lituanie identifiees precedemment mais dont la classification avait ete negligee. Le sous-groupe 16SrXXI-E a ete decouvert a partir de mycoplasmes nouvellement identifies chez les pucerons qui servent de vecteurs. D'autres etudes portant sur des tests de transmission par ces pucerons fourniront des informations sur l'epidemiologie et le pathosysteme des maladies du pin causees par des phytoplasmes, ainsi que sur la gestion de la maladie. [Traduit par la Redaction] Mots-cles: diversite genetique, phytopathogenes transmis par des insectes, puceron., 1. Introduction Phytoplasmas, previously known as mycoplasma-like organisms (MLOs), are minute cell-wall-less and phloem-restricted intracellular bacteria that infect a wide variety of plant species worldwide, including agronomically important crops and [...]

Abstract Fusarium graminearum is the main causal agent of Fusarium head blight (FHB) of small grain cereals, but the importance of weeds in the FHB disease cycle and the establishment of F. graminearum in agroecosystems are still not fully understood. The objective of this study was to determine the potential role of weeds present within cereal crop rotations as alternative hosts. F. graminearum was isolated from different organs of asymptomatic weeds sampled from six fields with cereal-crop rotations in Lithuania for two consecutive years (2015 and 2016). The fungi were identified using morphological and molecular methods. Out of 57 weed species that were investigated, 41 (71.9%) harboured F. graminearum isolates. Twenty five weed species were identified as new, previously undocumented, hosts. The majority (73.3%) of the isolates of F. graminearum from this study belonged to the 15ADON genotype while a smaller proportion (23.4%) belonged to the 3ADON genotype. All F. graminearum isolates that were assessed induced FHB symptoms on artificially inoculated spring wheat tested in the field. [ABSTRACT FROM AUTHOR]