First report of ‘Candidatus Liberibacter solanacearum’ on carrots and celery in Spain, in association with Bactericera trigonica
In Spain, the presence of ‘Candidatus Liberibacter solanacearum’ (EPPO Alert List) on carrot (Daucus carota) crops has recently been reported from the mainland and the island of Tenerife (Islas Canarias). The pathogen was also found in association with Bactericera trigonica, which was not previously reported as a potential psyllid vector.
Comunidad Valenciana, Castilla-La Mancha
In summer 2008, symptoms resembling those of ‘Ca. L. solanacearum’ were observed in several commercial carrot fields severely infested with psyllids (Bactericera sp.). These fields were located in the provinces of Alicante (18 fields – approx. 62 ha) and Albacete (52 fields – 297 ha), in the regions of Comunidad Valenciana and Castilla-La Mancha, respectively. Similar symptoms were observed in the following years (i.e. 2009, 2010 and 2011). Molecular tests detected the presence of ‘Ca. L. solanacearum’ in 1, 12 and 12 symptomatic carrot samples collected in 2008, 2009, 2010 respectively. The presence of Spiroplasma citri and Aster yellows phytoplasma was also detected in some samples. Comparison studies of DNA sequences showed a 97-99% similarity between the sequences of ‘Ca. L. solanacearum’ obtained from Spain and Finland.
In 2009 and 2010, commercial carrot fields in Tenerife (Islas Canarias, Spain) showed symptoms of leaf curling, discoloration of the foliage (yellow, bronze to purple), stunting of shoots and tap root, and proliferation of secondary roots. In diseased fields, large populations of the psyllid Bactericera trigonica were observed. A total of 18 petiole samples from symptomatic carrots were collected (13 in 2009 and 5 in 2010), as well as 3 samples (groups of 5 individuals) of B. trigonica. Molecular tests detected the presence of ‘Ca. Liberibacter solanacearum’ in 16 symptomatic carrot samples and 3 psyllid samples. Comparison studies of DNA sequences showed a 99% similarity between the sequences of ‘Ca. L. solanacearum’ obtained from Tenerife and Finland, and 98% similarity with sequences obtained from tomato in New Zealand.
Further records on celery and another region (Castilla León)
More recently, the NPPO of Spain has confirmed the detection of ‘Ca. L. solanacearum’ on carrot and celery (Apium graveolens) crops in the regions of Castilla-La Mancha, Castilla León and Comunidad Valenciana, as well as on carrot crops in Tenerife (Islas Canarias). The NPPO also pointed out that further diagnostic studies are still needed to confirm the identity of the pathogen, as only one type of molecular tests was used so far. In addition, the role of ‘Ca. L solanacearum’ in the symptomatology observed needs to be further studied as the bacterium has often been found in association with S. citri and other phytoplasmas. Therefore, research is currently being carried out in Spain on the detection and identification of ‘Ca. L. solanacearum’ and its symptomatology.
Alfaro-Fernández A, Siverio F, Cebrián MC, Villaescusa FJ, Font MI (2012) ‘Candidatus Liberibacter solanacearum’ associated with Bactericera trigonica-affected carrots in the Canary Islands. Plant Disease 96(4), p 581-582.
Alfaro-Fernández A, Cebrián MC, Villaescusa FJ, Hermoso de Mendoza, A, Ferrándiz JC, Sanjuán S, Font, MI (2012) First report of ‘Candidatus Liberibacter solanacearum’ in carrot in mainland Spain. Plant Disease 96(4), p 582.
NPPO of Spain (2011-10).