Inheritance of Branching in Sunflowers, Helianthus annuus L.¹

The inbred parental lines in this study were derived from varieties of sunflowers grown for their large edible seed ( Helianthus annuus var macrocarpus (DC.) Ckll.) and from the wild type H. annuus ssp. annuus . A classification using the following types was found to be adequate for genetic studies of branching in sunflowers: 0 ‐ no branching, 1 ‐ basally branched, 2 ‐ top branched, 3 ‐ fully branched with a central head, 4 ‐ fully branched without a central head (wild type). Four genes for branching were named in this study: the dominant gene Br2 for top branching; the duplicate dominant genes Br2 and Br3 from the wild type parent; and the recessive genes b2 and b3 which gave a fully branched phenotype only when homozygous for both genes. The single gene Y for green versus yellow growing point color was found to be linked with the gene Br3 for branching with 11.6 ± 1.0% recombination.