Big bud caused by several different phytoplasmas is an emerging threat to tomato production worldwide. The development of resistant varieties would be an effective approach to manage this problem, but it requires an appropriate screening technique. Recently, we have described a simple and efficient chip graft inoculation assay (CGIA) for the first time to screen tomato germplasm against Tomato leaf curl New Delhi virus. The present study was conducted to first validate the CGIA for phytoplasma transmission, then to assess the resistance of 74 genotypes belonging to different Solanum species against 16SrII-D phytoplasma. CGIA success rate and phytoplasma transmission was 100% since all the grafts survived and phytoplasma was detected in these plants using nested polymerase chain reaction. No genotype was found resistant as all the grafted plants showed typical disease symptoms. In addition to phytoplasma transmission, CGIA can be used for better understanding the plant–phytoplasma interactions and biology of phytoplasmas in tomato.

Phytoplasmas are insect-vectored pathogens that cause characteristic and destructive diseases in carrots and other vegetables. A phytoplasma disease was first observed in Israeli carrot fields in 1995. Analysis of infected carrots showed the presence of aster yellows and western-X phytoplasmas. In this study, commercial and experimental fields in the western Negev region of Israel were monitored for three years using yellow sticky traps and vacuum sampling. Potential vectors of leafhoppers and planthoppers were analysed by PCR for the presence of phytoplasma DNA. Infected plants were also assayed for phytoplasma DNA. Extracted phytoplasma DNA was subjected to RFLP analysis to determine groups to which the phytoplasmas belonged. It was determined that carrots and leafhoppers from the experimental station were infected with a phytoplasma belonging to the Elm Yellows (EY) group; this is the first report of EY infecting carrots. Based on our findings, the two most probable insect vectors are Circulifer haematoceps complex (Mulsant & Rey) and Neoaliturus fenestratus (Herrich-Schäffer).