Background. Sunflower seed production is based on utilization of the heterosis effect, manifesting itself in improving both yield and plant height in hybrids. Short-stemmed lines need to be used to develop commercial hybrids with an optimum height. Molecular bases of the trait manifestation in the dwarf lines from VIR’s sunflower genetic collection have not yet been studied. Materials and methods. The material included 27 short-stemmed and 10 tall sunflower lines from VIR’s genetic collection, as well as the F₁ and F₂ hybrid generations derived from crossing the tall (VIR 340) and dwarf (VIR 171) genotypes. The parental lines and hybrids were phenotyped for plant height, leaf number, and internode length. Genotyping for the Rht1 locus (HaDella1 candidate gene), encoding the negative regulator of the gibberellin response, the DELLA protein, was performed using the developed CAPS marker. Results. The average plant height in the VIR 340 line over a three-year study was 162 cm, the number of leaves 29, and the internode length 6 cm. The VIR 171 line demonstrated the plant height of 66 cm, leaf number of 24, and internode length of 2.8 cm. The F₁ hybrids were uniform, with the height of 180–190 cm, that indicated the dominance of the long stem trait. Analyzing the segregation in the F₂ hybrid generation led to an assumption admitting the digenic control of the dwarf phenotype in the VIR 171 line. The CAPS marker G-D-1/ Bmt I was developed to identify a missense mutation T>C in the first exon of the HaDella1 gene, which results in the substitution of leucine with proline in the DELLA motif. Using the marker, the mutant Rht1 allele was identified in the VIR 171 and VIR 434 dwarf lines, similar in their origin and phenotype. The results of validation in the F₂ hybrid population (VIR 340 × VIR 171) confirmed the efficiency of the G-D-1 / Bmt I marker for selecting dwarf genotypes homozygous for the Rht1 mutant allele.

For sunflower (Helianthus annuus L.) hybrid breeding, we evaluated 54 paternal lines crossed with three cytoplasmic male-sterile testers. The 162 hybrids were grown for two years at one location and analysed with a plot-level mixed model that separates genotype × year terms. Baker’s ratio was 0.958 for oil content, 0.951 for 1000-seed weight and 0.933 for plant height, and the heritability of the hybrid mean 0.90 and 0.91 for the first two. Without the two confectionery lines, Baker’s ratio for these traits remained 0.877 and 0.907 and heritability 0.72 and 0.83. Paternal general combining ability (GCA) for oil content, 1000-seed weight, plant height and flowering time agreed between the two seasons (concordance 0.71–0.85). For seed yield, additive control was not established (Baker’s ratio 0.440, 95% interval 0.00–0.82); plot error was 3.6 times the genetic variance and paternal GCA was weakly repeatable (r = 0.24). VK101A raised oil content, VK934A 1000-seed weight and plant height, and VA761A lowered plant height. A composite index identified LI18, LI41, LI6, LI53 and LI19 as candidate donors. Paternal lines can be selected on GCA for these three traits; seed yield and the ranking of donors that depends on this yield require testing in more environments.

Background/Objectives: Sunflower (Helianthus annuus L.) paternal lines are evaluated by testcrossing over several seasons. We asked how well parental genotypes predict the general combining ability (GCA) of an untested line. Methods: Fifty-four paternal lines and three cytoplasmic male-sterile testers were genotyped by sequencing. Their 162 hybrids were phenotyped for two years at one site and genotyped in silico. Genomic best linear unbiased prediction (GBLUP) was evaluated on the 52 oilseed lines by holding out each line with its hybrids. Results: Predictive ability for paternal GCA was 0.66 for 1000-seed weight, 0.40 for oil content, 0.47 for seed yield, and 0.48 for oil yield. Gains beyond about 30 training lines were unclear within this panel, with small test sets at the largest sizes. Parental distance correlated weakly with hybrid yield (r = 0.31), and additive scans found no significant associations. A chromosome 14 candidate for 1000-seed weight had a dominance deviation of +3.38 g, but five-trait-adjusted p-values were 0.047 (bootstrap) and 0.052 (within-tester permutation). Inferred hybrid heterozygosity follows parental combinations, preventing separation of locus-specific dominance from parental-combination effects. Conclusions: These within-panel results support further evaluation of genomic preselection, especially for 1000-seed weight. Neither training-set size nor predictive performance is established for other populations or environments; the chromosome 14 candidate requires independent validation.

To choose paternal lines for sunflower (Helianthus annuus L.) hybrids, we evaluated 54 paternal lines crossed with three cytoplasmic male-sterile (CMS) testers. The 162 hybrids were grown for two years and analysed with a plot-level mixed model that separates genotype × year terms. Baker’s ratio was 0.958 for oil content, 0.951 for 1000-seed weight and 0.933 for plant height, and the broad-sense heritability of the hybrid mean was 0.90 and 0.91 for the first two. Without the two confectionery lines, Baker’s ratio for oil content and 1000-seed weight remained 0.877 and 0.907 and heritability 0.72 and 0.83. Paternal general combining ability (GCA) for both traits was repeatable between years (r = 0.75 and 0.85). For seed yield, additive control was not established (Baker’s ratio 0.440, 95% interval 0.00–0.82): plot error exceeded the genetic variance 3.6-fold, and paternal GCA was weakly repeatable between years (r = 0.24). VK101A raised oil content, VK934A 1000-seed weight and plant height, and VA761A lowered plant height. A composite index identified LI18, LI41, LI6, LI53 and LI19 as candidate donors. Paternal lines can be selected on GCA for oil content, 1000-seed weight and plant height; seed yield requires testing in more environments.