Estimates of genetic diversity can be based on different types of data. The aim of this research were to study genetic diversity among Croatian wheat cultivars by random amplified polymorphic DNA (RAPD) markers, morphological traits and pedigree records; to analyse differences between wheat cultivars from two breeding centres; and to evaluate usability of RAPD markers for estimation of genetic diversity among wheat cultivars in comparison with morphological traits and pedigree record data. Studies were conducted on 14 wheat cultivars and breeding lines from two breeding centres in Croatia. For the RAPD analysis 36 primers were screened and the 14 most polymorphic ones yielded 341 polymorphic bands. Twelve morphological traits were used for morphological analysis. Pedigrees were composed of seven generations of ancestors. RAPD markers showed a high level of polymorphism among the cultivars examined and the breeding lines. No significant correlations were observed among the methods tested.

Six Trifolium pratense L. cultivars, five diploid and one tetraploid, were grown in the lowland region (123 m altitude) and the mountain region (650 m altitude). Dry ma�er (d.m.) and green mass (g.m.) yield, stem height and leaf proportion were assessed from each of the three growing seasons. Chemical composition was assessed from the average samples of all cuts in the second year of the experiment. Greater green mass (54.14 t/ha) and dry ma�er yield (9.86 t/ha), stem height (0.61 m), crude protein (157.6 g/kg), crude fiber (222.9 g/kg), crude ash (100.68 g/kg) and crude fat (30.09 g/kg) content were observed in the mountain region, compared to the lowland region (45.61 t/ha g.m. 8.92 t/ha d.m. 0.59 stem height, 156.38 g/kg crude protein, 216.6 g/kg crude fiber, 94.85 g/kg crude ash, 24.98 g/kg crude fat). The greater leaf proportion (47.2%) and nitrogen free extract content (420.13 g/kg) were observed in the lowland region compared to the mountain region (42.95% and 402.99 g/kg, respectively). A significant location × cultivar interaction was found for all investigated parameters except for leaf proportion.

Maksimir 3 Synthetic (M3S) maize population was developed at the Faculty of Agriculture University of Zagreb by intercrossing inbred lines, whose origins trace back to several open-pollinated varieties and local populations from different regions of the former Yugoslavia. The population was subjected to two cycles of selfed progeny recurrent selection for grain yield. The objectives of this study were: (i) to determine genetic distances among the parental inbred lines of the M3S population (M3S progenitors), the M3S population before and after two cycles of recurrent selection, and elite inbred lines representing the BSSS and Lancaster heterotic group; and (ii) to examine the effect of two cycles of recurrent selection on allele frequency changes in the population. Nine M3S progenitors, three BSSS lines, and three Lancaster lines were genotyped at 24 SSR loci, out of which nine randomly chosen loci were used for genotyping 96 individuals from both C0 (the M3S population before selection) and from C2 (M3S population after two cycles of selection). A total of 101 alleles were detected across 24 loci in the 15 lines, whereas 83 alleles were found in the nine M3S progenitors. Among the latter 83 alleles 31 were unique, i.e. found only in one of the progenitors. Mean genetic distance among nine M3S progenitors was 0.61 indicating a broad genetic base of the M3S population. High mean genetic distance was found between M3S progenitors and BSSS lines (0.69) and M3S progenitors and Lancaster lines (0.71). This indicates that the M3S population represents a germplasm source unrelated to both the BSSS and Lancaster germplasm. Mean genetic distance between the M3S population and BSSS as well as Lancaster lines decreased slightly after two cycles of recurrent selection suggesting the need to introduce testers from both groups in future selection in the M3S population in order to maintain heterotic complementarity of the M3S population to these groups. A test of selective neutrality identified several non-neutral loci in the population whose allele frequency changes from the C0 to the C2 cannot be explained by genetic drift. The majority of nonneutral alleles, whose frequency increased after two cycles of selection, were present in at least one line from the BSSS or Lancaster heterotic group.

S. SIKORA, S. REDŽ EPOVIĆ , I. PEJIĆ A N D V . K O ZU MP L IK . 1997. RAPD fingerprinting was used for strain identification and the assessment of genetic diversity within a field population of Bradyrhizobium japonicum. Total genomic DNAs from 13 field isolates and two inoculant strains were amplified using six different 10-mer primers. Different and informative band patterns were obtained for all strains analysed. Cluster analysis unexpectedly revealed that none of the field isolates was identical to inoculant strains which were regularly used for soybean inoculation. Among field isolates two highly divergent groups were determined. The results indicate that RAPD is a very discriminative and efficient method for differentiating and studying genetic diversity of B. japonicum strains.

The dissemination of orchard-grass