First report of ‘Candidatus Liberibacter solanacearum’ haplotype C in a symptomless potato plant in Finland
In Finland, ‘Candidatus Liberibacter solanacearum’ haplotype C is transmitted by the carrot psyllid Trioza apicalis (Hemiptera: Triozidae) and causes yield losses (see EPPO RS 2012/118 and 2017/129). Because ‘Candidatus Liberibacter solanacearum’ haplotypes A and B (EPPO A1 List) cause the damaging zebra chip disease in potato in the USA and New Zealand, the occurrence of ‘Ca. Liberibacter solanacearum’ in cultivated and volunteer potatoes in Tavastia Proper and Satakunta regions of Finland was studied. Eight volunteer potato plants and one cultivated potato plants grown at the edge of a carrot field were tested by PCR and found to be positive for ‘Ca. L. solanacearum’ haplotype C but did not show symptoms of zebra chip disease. This is the first observation of haplotype C in field grown potatoes. It may be noted that haplotype E was also detected in potato stores in Spain (see EPPO RS 2017/134). Transmission experiments were performed. Attempts to transmit ‘Ca. L. solanacearum’ into potato with T. apicalis were not successful. ‘Ca. L. solanacearum’ haplotype C was transmitted from infected carrots to potato plants by leaf grafting and by phloem connection formed by dodder but daughter tubers produced by the infected potato plants all tested negative.
Sources
Haapalainen M, Latvala S, Rastas M, Wang J, Hannukkala A, Pirhonen M & Nissinen AI (2018) Carrot pathogen ‘Candidatus Liberibacter solanacearum’ haplotype C detected in symptomless potato plants in Finland. Potato Research 61(1), 31–50. https://doi.org/10.1007/s11540-017-9350-3