Survey of Candidatus Liberibacter Solanacearum and Its Associated Vectors in Potato Crop in Spain

SIMPLE SUMMARY: Zebra chip disease (ZC) in potato is an economically important disorder, documented in North and Central America and New Zealand. It is associated with the bacterium ‘Candidatus Liberibacter solanacearum’ (CaLsol), which is transmitted by the psyllid Bactericera cockerelli. The characteristic symptom of ZC is a dark and light striped pattern in chips, making them commercially unacceptable. Naturally CaLsol-infected potato tubers were reported in Europe, where the threat of ZC for European potato crops is a major concern. This work studied the presence and abundance of ZC symptoms and CaLsol in potato plants, as well as those psyllid species that eventually could transmit the bacterium, in the main producing areas in Spain. Very few symptomatic and CaLsol-positive plants were detected in Mainland Spain, and any positive plant was detected in the Canary Islands. Most of the adult psyllids captured were identified as Bactericera nigricornis, and some of them as Bactericera trigonica, but no B. cockerelli was detected. B. nigricornis was found widely distributed in the northern half of the Iberian Peninsula, and it was the only one able to feed and reproduce on potato plants. However, this psyllid does not seem sufficient to pose a threat to potato production, due to the scarce number of specimens and because the frequency of B. nigricornis specimens that were CaLsol+ was very low. ABSTRACT: ‘Candidatus Liberibacter solanacearum’ (CaLsol), the etiological agent of potato zebra chip (ZC), is transmitted to potato plants by the psyllid Bactericera cockerelli (Šulc, 1909) in North and Central America and New Zealand. The risk of the dispersion of ZC in Spain depends on the presence of an efficient vector. This work studies the presence and abundance of ZC symptoms and CaLsol in potato plants, as well as the presence and abundance of psyllid species associated with potato crops in the main producing areas in Spain. Eighty-eight plots were surveyed punctually to detect ZC symptoms and psyllid species in the main potato-producing areas. Furthermore, fourteen potato plots were surveyed by different sampling methods during the cropping season to detect psyllid species from 2016 to 2018. Very few symptomatic and CaLsol-positive plants were detected in Mainland Spain, and any positive plant was detected in the Canary Islands. Most of the adult psyllids captured were identified as Bactericera nigricornis (Foerster, 1848), and some of them as Bactericera trigonica, but no B. cockerelli was detected. B. nigricornis was found widely distributed in the northern half of the Iberian Peninsula; however, this psyllid does not seem sufficient to pose a threat to potato production, due to the scarce number of specimens and because the frequency of B. nigricornis specimens that were CaLsol+ was very low.