SUMMARYKnowledge of genetic diversity of confectionary sunflower can have a large impact on its use in breeding programmes. However, levels and distribution of genetic variation within the confectionary sunflower gene pool are still not adequately explored. The aim of the present paper was to describe the diversity of 68 confectionary sunflower genotypes: open-pollinated varieties, lines and hybrids. A total of 32 morphological traits were used for characterization. The Shannon & Weaver diversity index (H) was estimated as a measure of morphological diversity. The mean value of the Shannon index was 0·71, which indicates a high morphological diversity. The lowest diversity was found for leaf descriptors, moderately high to high for seed traits, while the highest values were found for disc flowers and ray florets. The highest individual descriptor diversity was found for: head attitude, the angle of leaf lateral nerves and ray floret disposition. The homogeneity analysis (HOMALS) multivariate reduction technique for nominal categorical data proved to be an efficient method for a comprehensive overview of genotype diversity and group homogeneity. Besides diversity, the number of categories and uniformity of genotype distribution determines discriminative power of descriptors. Traits that contributed the most to the distinction of genotypes were identified, enabling differentiation of genotypes with similar phenotypic attributes. The highest discriminative power was observed in traits such as anthocyanin colouration of stigma (DFIA), seed colour of stripes and seed main colour. The genotypes tested formed two distinctive major groups of varieties and hybrids with inbred lines widely dispersed along both axes. A separate grouping was obtained per the most discriminative traits based on HOMALS analysis, while the best separation was obtained using DFIA. Isolated genotypes that may not be representative by yield or seed-specific traits can be useful sources of traits for breeding. Morphological characterization can be used to improve description and classification of confectionary sunflower germplasm when evaluating diversity.

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Oil yield is a major characteristic of each sunflower hybrid (Škorić et al., 2005). To be able to develop new high-oil sunflower hybrids by the method of interspecific hybridization, it is necessary to have information on mode of inheritance and combining abilities of inbred lines used. When selecting prospective lines as components of future hybrids, it is important to know correlations between yield components on one side and oil content on another.Seven new divergent cytoplasmic male sterile lines (A) developed by interspecific hybridization, three Rf-restorer lines used as testers and 21 F 1 hybrids have been subjected to the line × tester analysis. Significant differences have been obtained in mean values for all characteristics under study.Significant differences were found between A lines and R lines on one side and their F 1 hybrids on the other in oil content, plant height, head diameter, total number of seeds per head, 1000-seed weight and seed yield per plant. The line NS-GS-4 exhibited a highly significant positive GCA value for oil content. The line NS-GS-5 had a highly significant negative GCA value for oil content. The hybrid NS-GS-6 × RHA-R-PL-2/1 had a highly significant positive SCA value for oil content. Non-additive component of genetic variance played the main role in the inheritance of oil content, as indicated by the analysis of variance of combining abilities and the analysis of components of genetic variance. Further confirmation was the ratio GCA/SCA for oil content in the F 1 generation which was smaller than unity (0.33). The highest average contribution to the expression of oil content (77.3%) was exhibited by the A lines. Highly significant negative correlations were found between oil content on one side and head diameter, total number of seed per head, 1000-seed weight and seed yield per plant on the other.

The creation of new sunflower hybrids with high genetic potential for seed yield on the basis of interspecies hybridization requires a possession of the information about the mode of inheritance and the combining abilities of the created inbreed lines for the total seed number per head and the mass of 100 seeds. Apart from this the research of interdependence between yield components and seed yield allows the defining of traits which have the biggest influence on the yield formation. Significant differences were found among the A lines, Rf testers and their F1 hybrids in total seed number per head and the mass of 100 seeds. Analysis of variance of the combining abilities revealed highly significant differences for GCA and SCA. Highly significant positive value GCA was demonstrated by A-line NS-GS-5 for both traits. Hybrid NS-GS-5xRHA-R- PL-2/1 has the highest significant value SCA for both traits. The main role in inheritance of the total seed number per head and the mass of 100 seeds is played by non additive component of the genetic variance which is confirmed by the GCA/SCA relation in F1 generation that is less than one (0.11, 0.24). Rf-testers had the highest average contribution in the expression of the total seed number per head (55.8%) while for the mass of 100 seeds a more significant contribution was given by A-line (70.6%). A strong positive interdependence has been determined between seed yield and total seed number per head (0.37

Path coefficient analysis was used to separate direct and indirect effects of studied traits on seed oil content and seed yield, and to identify traits that could be used as selection criteria in sunflower breeding. Significant and highly significant correlations were found between most of the examined traits. Highly significant negative correlations have been established between stem diameter, total leaf area per plant, head diameter and 1,000-seed weight on one side and seed oil content on the other. Highly significant positive correlations have been established between seed yield on one side and stem diameter, total leaf area per plant, head diameter, total number of seeds per head, and the 1,000-seed weight on the other. The weight of 1,000 seeds had a highly significant direct negative effect on seed oil content and a highly significant direct positive effect on seed yield. The total number of seeds per head has demonstrated a highly significant direct positive effect on seed yield and oil content. The total leaf number per plant has demonstrated a significant direct positive effect on seed yield. A path coefficient analysis of seed yield at phenotypic level indicated that maximum direct effects were shownby the weight of 1,000 seeds, total number of seeds per head and total leaf number per plant. The total number of seeds per head was the most important trait that determined seed yield and oil content. The obtained results can be used in sunflower breeding programs aimed at the development of sunflower hybrids that combine high genetic potentials for seed yield and seed oil content.