Phenolic Compounds and Peroxidases in Sunflower Near-Isogenic Lines After Downy Mildew Infection

Two near-isogenic lines of sunflower, resistant (+Pl6 gene) and susceptible (-P16 gene) to downy mildew were used in this paper. Secondary infection with a suspension of Plasmopara halstedii spores was done on the plants in the phase of first pair of leaves. In the samples taken 12 h after infection, content of phenolic compounds in methanolic extracts from frozen leaves was analysed by HPLC. POD activity was determined spectrophotmetrically and POD isoforms by isoelectrophoresis. Constitutive level of phenolic compounds and their accumulation after infection were higher in the susceptible than in the resistant line. Increased POD amount in leaf, constitutively present in NS-H-26R, was in correlation with increased guaiacol-dependent POD activity and low total phenolics contents. After infection, guaiacol- and chlorogenic acid-dependent POD activity significantly increased in both lines. Scopoletin-dependent POD activity was induced upon infection only in NS-H-26R. IEF electrophoresis revealed existance of four anionic isoforms of peroxidase in leaves of both lines. The main isoform with pI 5 was particularly intesified in the resistant line. In conclusion, scopoletin-dependent POD activity that was induced upon infection only in resistant NIL indicates a specific role of POD in coumarin metabolism that is possibly connected with the presence of Pl6 gene

Relationship between genetic distance and heterosis based on quantitative traits and SSR markers in sunflower

The objective of this study was to determine the relationship between SSR based genetic distance (GD) of new NS sunflower inbred lines for most important agronomic traits and heterosis. Twenty three sunflower inbred lines (twenty restorer lines and three female lines used as testers) were selected based on their diverse genetic background for plant height, head diameter, thousand seed mass, oil content, seed yield per plant and oil yield per plant. Significant heterosis was observed in hybrid combinations for all examined traits except oil content. Genetic distance between pairs of tested sunflower inbred lines ranged from 0.13 to 0.8. There was no significant positive correlation between genetic distance and mid- and better-parent heterosis, specific combining ability and mean value in any of the examined traits for all 60 hybrids. A highly significant negative correlation was found between GD and mean oil percentage (r=-0.33 p<0.01). However significant correlations between GD and better-parent heterosis for thousand seed weight were found for hybrids of the tester line HA-19 (r=0.43 p<0.05) and between GD and mid-parent heterosis for plant height for hybrids of the tester line HA-26 (r=0.47 p<0.05). Although GD was generally a poor predictor of heterosis, better results are obtained if hybrid combinations for each tester and each trait are analyzed separately

The wild sunflowers collection in Novi Sad

Lowered genetic variability in the cultivated sunflower and use of interspecies hybridization in sunflower breeding were the main reasons to establish the wild species collection. Wild species were collected during collecting trips performed jointly by researchers from Novi Sad and Fargo from 1980 to 1991. A total of 917 accessions were gathered. Different numbers of species (1-37) and populations (52-384) were gathered in each trip and wild sunflower habitats were inspected in 6-21 US federal states. Presently there are 21 perennial and 7 annual species in the collection, represented by 447 accessions. The perennial species are grown in quarantine fields (311 accessions) and kept in temporary seed storage at +4° (163 accessions). Annual species are sawn each year and 136 accessions are kept in temporary seed storage. Seed reserves vary from a few seeds to several thousand per accession and all of them were produced in the period between 1998 and 2004. Several problems were encountered in the course of the establishment maintenance and utilization of the collection: 1. Occasional errors in species determination during collection trips were caused by the presence of natural hybrids, heterogeneity of natural populations and differences in ploidy within the same species; 2. The local continental climate caused loss in material due to winterkill and inability of some species to complete the vegetative cycle; 3. Perennial species were difficult to grow because of low seed viability; 4. Low self-fertility or complete selfsterility precluded seed production and renewal of seed reserves; 5. Wild species were difficult to utilize as a source of desirable genes because of their cross incompatibility with cultivated sunflower. The collection of wild sunflower species has mostly been used for development of disease resistant or tolerant genotypes, new cms and Rf genes and for breeding of special-purpose hybrids