“Candidatus Liberibacter solanacearum” infection of commercial tomatillo, Physalis ixocarpa Brot. (Solanales: Solanaceae) in Saltillo, Mexico

The potato psyllid, Bactericera cockerelli (Šulc), (Hemiptera: Triozidae) is a pest of Solanaceous crops (Solanales) including potato (Solanum tuberosum L.) and tomato (Solanum lycopersicum L.). Feeding by high populations of nymphs causes psyllid yellows while adults and nymphs are vectors of the plant pathogen, “Candidatus Liberibacter solanacearum” (Lso). Foliar symptoms that were consistent with either Lso-infection or psyllid yellows were observed in 2019 on tomatillo (Physalis ixocarpa Brot.; Solanaceae) grown within an experimental plot located near Saltillo, Mexico. This study had three primary objectives: 1) determine whether the foliar symptoms observed on tomatillo were associated with Lso infection, 2) identify the haplotypes of Lso and potato psyllids present in the symptomatic plot, and 3) use gut content analysis to infer the plant sources of Lso-infected psyllids. Results confirmed that 71% of symptomatic plants and 71% of psyllids collected from the plants were infected with Lso. The detection of Lso in plants and psyllids, and the lack of nymphal populations associated with psyllid yellows strongly suggests that the observed foliar symptoms were caused by Lso infection. All infected plants and insects harbored the more virulent Lso haplotype B, but one psyllid was also co-infected with haplotype A. The potato psyllids were predominantly of the central haplotype, but one psyllid was identified as the western haplotype. Molecular gut content analysis of psyllids confirmed the movement of psyllids between non-crop habitats and tomatillo and indicated that Lso infection of psyllids was associated with increased plant diversity in their diet.