engleski

Dianthus croaticus Borb.-a new host for phytoplasmas from ribosomal groups 16SrI and 16SrIII

Dianthus croaticus Borb. (Caryophyllaceae) is an endangered neo-endemic Croatian species found mainly in the northwestern part of the country. The Croatian carnation seeds were collected from two locations in the Zagreb area throughout the years 2001-2003. The cultivation in pots under the greenhouse conditions has been attempted in order to preserve this species and to investigate the possibility of its introduction in the market. The plants grown in the greenhouse started to display an array of different symptoms resembling those of phytoplasma infection. Several plants exhibited stunting, compact growth and leaf curling, unlike the others that had shortened and pointed leaves. Some plants had narrow leaf blades and, for the majority of the plants described, symptoms were accompanied by leaf colour changes (reddening or yellowing). Nucleic acids were extracted from D. croaticus seeds and various leaf tissue samples to be used in direct and nested PCR experiments. Amplification of phytoplasma 16S rRNA gene was performed in a direct PCR by using R16F1/R0 and/or P1/P7 universal phytoplasma primer pairs. The nested PCRs were performed by using R16F2/R2, 16R738f/R1232r, as well as group-specific R16(I)F1/R1 and R16(III)F2/R1 primers. Amplified portions of 16S rDNAs from all nested PCR assays were subjected to digestions with restriction enzymes MseI(=Tru9I), AluI, KpnI and TspEI. RFLP analyses revealed phytoplasma patterns corresponding to those of standard strains from ribosomal groups I and III in seeds as well as in symptomatic and symptomless plants. Phytoplasma isolates from D. croaticus belonging to ribosomal group I are characterized in detail by PCR-RFLP analyses of other gene regions such as: tuf, BB88 and ribosomal protein rpL22 gene. Further investigation on plants cultivated in vitro from seeds already included in this study is in progress in order to test the phytoplasma presence.

phytoplasmas; Dianthus croaticus Borb.; ribosomal groups 16SrI; 16SrIII; mixed infection; PCR; RFLP

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