Multigene analysis for differentiation of aster yellows phytoplasmas infecting carrots in Serbia

Abstract

During a Survey of large cat-rot fields in Serbia, plants showing leaf reddening and/or yellowing, adventitious shoot production and reduction ill taproot size and quality were observed ill a low percentage of plants. To verify phytoplasma association with the described symptoms and to carry out pathogen differentition, PCR assays followed by restriction fragment length polymorphism (RFLP) analyses and/or sequencing of phytoplasma 16Sr DNA and ribosomal protein genes 122 and s3, tuf, putative aa kinase plus ribosomal recycling factor genes and DNA helicase gene were carried Out. Phytoplasmas belonging to 16Srl-A and 16Srl-B ribosomal subgroups and to rpI-A and rpI-B ribosomal protein Subgroups, respectively, were identified by RFLP analyses in 13 of 15 sympotomatic plants tested. No amiplification was obtained with non-symplomatic carrot samples. The identification was confirmed by sequence analyses of the phytoplasma genes Studied. in two carrot samples, presence of interoperon sequence heterogeneity was detected and phytoplasma strains were identified as belonging to 16SrI group but were not assigned to any 16S rRNA or ribosomal protein subgroup. This research allowed the first molecular identification of phytoplasmas infecting carrot in Serbia using several molecular markers, and it indicates that under field conditions in non-epidemic Outbreaks a certain amount of genetic mutation may occur in conserved genes of these prokaryotes.