Clonal structure of Rubus chamaemorus populations: comparison of different molecular methods

The clonal structure of Rubus chamaemorus populations was investigated using DNA fingerprinting. The PCR-based methods included the use of 10-base RAPD primers and 16-base simple sequence repeat primers. In the hybridization method variation was studied using hypervariable multilocus probes, one derived from the M13 bacteriophage and the other a synthetic (AC)/(TG) polynucleotide. Although R. chamaemorus expresses clear variation in morphology, the level of genetic differentiation appears to be fairly low. The observed numbers of clones in the three populations examined in Finland varied from 2 to 4. The total number of genotypes across populations was 5, of which one was unique. The results obtained using the two fingerprinting methods were comparable but lead to a slightly different grouping of clones.     

TRIM retrotransposons occur in apple and are polymorphic between varieties but not sports

Retrotransposon markers have been demonstrated to be powerful tools for investigating linkage, evolution and genetics diversity in plants. In the present study, we identified and cloned three full-size TRIM (terminal-repeat retrotransposon in miniature) group retrotransposon elements from apple (Malus domestica) cv. ‘Antonovka’, the first from the Rosaceae. To investigate their utility as markers, we designed primers to match the long terminal repeats (LTRs) of the apple TRIM sequences. We found that PCR reactions with even a single primer produced multiple bands, suggesting that the copy number of these TRIM elements is relatively high, and that they may be locally clustered or nested in the genome. Furthermore, the apple TRIM primers employed in IRAP (inter-retrotransposon amplified polymorphism) or REMAP (retrotransposon-microsatellite amplified polymorphism) analyses produced unique, reproducible profiles for 12 standard apple cultivars. On the other hand, all seven of the sport mutations in this study were identical to their mother cultivar. Genetic similarity values calculated from the IRAP/REMAP analyses or the STMS (sequence tagged microsatellite sites) analysis were generally comparable. PAUP cluster analysis based on IRAP and REMAP markers in apple and Japanese quince generated an NJ tree that is in good accordance with both a tree based on SMTS markers and the origin of the studied samples. Our results demonstrate that, although they do not encode the proteins necessary to carry out a life cycle and are thereby non-autonomous, TRIMs are at least as polymorphic in their insertion patterns as conventional complete retrotransposons. Kristiina Antonius-Klemola, Ruslan Kalendar are the first two authors contributed equally to this work