Haplotypes and vectors of ‘Candidatus Liberibacter solanacearum’ in Scotland (United Kingdom)
‘Candidatus Liberibacter solanacearum’ is a bacterium known to cause diseases in Apiaceae crops in Europe and in potato and other Solanaceae crops in North and Central America and in New-Zealand. Potato haplotypes are listed in EPPO A1 List. In the United Kingdom, ‘Ca. L. solanacearum’ haplotype C was first detected in Trioza anthrisci (Hemiptera: Triozidae) collected by suction traps (RS 2018/009) but not in crops. Further research was conducted on potential vectors of ‘Ca. L. solanacearum’ (Lso) and on the haplotypes present in carrot (Daucus carota) crops in Scotland. Four Lso haplotypes were found: C, U, and two novel haplotypes in plants or psyllids. Lso haplotype C was found in a small percentage of asymptomatic carrot plants from a field where known vectors of this haplotype were not found. This is the first report of Lso in cultivated carrot growing in the United Kingdom.
Surveys for psyllids collected 535 specimens comprising 19 psyllid species in carrot fields and the surrounding vegetation. Trioza anthrisci was found to be present only in one municipality (Elgin, Moray council area) with 100% of individuals harbouring Lso haplotype C. Lso haplotype U was found at all sites in Trioza urticae and at some sites infecting the weed Urtica dioica. The two novel haplotypes were found in Craspedolepta nebulosa and C. subpunctata (both Hemiptera: Aphalaridae) and named Cras1 and Cras2. This is the first report of Lso in psyllids from the Aphalaridae family. These new haplotypes were most closely related to Lso haplotype H recently found in carrot and parsnip. Lso was also detected in several weed plants surrounding carrot and parsnip fields. These included two Apiaceous species Aegopodium podagraria and Anthriscus sylvestris, one Galium sp. (Rubiaceae) and Chenopodium album (Amaranthaceae).
Sumner-Kalkun JC, Highet F, Arnsdorf YM, Back E, Carnegie M, Madden S, Carboni S, Billaud W, Lawrence Z, Kenyon D (2020) ‘Candidatus Liberibacter solanacearum’ distribution and diversity in Scotland and the characterisation of novel haplotypes from Craspedolepta spp. (Psyllidae: Aphalaridae). Scientific Reports 10,16567. https://doi.org/10.1038/s41598-020-73382-9