Development of sulfonylurea (SU) group herbicide resistant cytoplasmic male sterile and maintenance ornamental sunflower lines

Sunflower (Helianthus annuus L.) is an annual species belonging to the Asteraceae family and has a widespread use as an oil plant, snack and ornamental plant. Although it is mostly used as cut flowers in the ornamental plants sector, it is also used as outdoor and indoor ornamental plants. Cytoplasmic male sterility (CMS), which has been used in the varieties developed in ornamental sunflower breeding in recent years, enables sterile hybrid variety breeding and easy and cheap hybrid seed production. Weeds compete with sunflowers, especially in the first developmental stage, and inhibit plant growth and development through allelopathic and shading effects. The aim of this study was to develop cytoplasmic male sterile and maintainer ornamental sunflower lines resistant to Sulfunilurea (SU) group herbicides in different flower colors and plant structures suitable for different uses such as outdoor and indoor (potted) and cut flowers. This study was initiated by crossing one SU-resistant Restorer (R) line with the sterile hybrid "Sunrich Orange F1" ornamental sunflower in the Akdeniz University Faculty of Agriculture Ornamental plants greenhouse. The F1 plants obtained were used as pollen sources and backcrossed to maintainer line B and 'Sunrich Orange F1'. Commercial 15 Fertil F1 ornamental sunflowers with different plant structure, colors, and flower characters were backcrossed (BC) to SU-resistant A and B lines at the BC1F1 stage. Backcrosses were continued and SU-resistant A and B lines were obtained at different generations (such as BC4F1, and BC3F1). A x B combinations were formed by giving pollen to A lines from SU-resistant B lines, which represent different genetic materials and have high ornamental plant potential, and sterile (CMS) lines were propagated with their own B (maintainer) lines. The morphological characteristics and ornamental potential of the hybrids obtained from the A x B hybrid combinations were evaluated. In this context; vase life, leaf size, leaf colour, flowering head and stem posture, petal density, petal posture, petal shape, flower stem length, overall plant height, flower diameter, disc diameter, flower stem diameter, pollen formation in disc flowers, branching status and shape, colour of ray and disc flowers were examined. In this study, for the first time in our country, SU herbicide resistant CMS and idameci ornamental sunflower lines were developed, which were used to obtain commercialised domestic hybrid ornamental sunflower variety candidates. At the end of the study lines, suitable for different uses such as cut flowers, potted ornamental plants and outdoor ornamental plants, with a wide range of colour tones and flower/plant structure with different plant architecture ranging from a very dwarf (30-40cm), multi-branched and compact structure to a single stem/branched and taller form were developed. The results showed that, four of the developed hybrid lines (BC1F1-F1E-1, BC1F1-F1G-13, BC1F1-F1K-6, and BC1F1-F1P-2) had a wide range of colors, a vase life of 13–15 days, flower stem lengths of 60–163 cm, flower stem diameters of 0.9–1.6 cm, and flower diameters of 11.2-14.5 cm. These characteristics imply that these hybrid lines might be viable commercial variety candidates for the cut flower industry. In addition to these hybrids, 7 and 5 sunflower lines with potential for use as outdoor and potted ornamental plants, respectively, were identified. It is predicted that these developed lines will provide significant contributions to the sector by increasing the species diversity in the ornamental plants sector.