Inheritance of floral colour and type in four new inbred lines of ornamental sunflower (Helianthus annuus L.)

Sunflower (Helianthus annuus L.) is grown commercially and as an ornamental plant. Floral colour and inflorescence type are important traits in the breeding of ornamental sunflower. Sunflowers consist of ray florets, which are arranged around the perimeter with disc florets in the centre. The colour of the ray florets can vary from various shades of red to lemon-yellow. The inheritance of ray floret colour was studied through diallel crossing of inbred lines with red, yellow, or lemon-yellow coloured florets. In the F-1 generations, the red colour was partially dominant over yellow and lemon-yellow ray florets, forming a 'Gaillardia' pattern, while yellow was dominant over lemon-yellow. The segregation ratios in the F-2 generations were 9:7 (red x yellow) and 3:1 (red x lemon-yellow and yellow x lemon-yellow), indicating control by one or two genes, respectively. The colour of the disc florets depended on the presence or absence of anthocyanin pigmentation. Disc florets that lacked anthocyanin pigmentation were usually different shades of yellow. Anthocyanin pigmentation was dominant over yellow and lemon-yellow, showing monohybrid inheritance with a segregation ratio of 3:1 in the F-2 generation. Chrysanthemum-type inflorescences had elongated disc florets. In crosses between chrysanthemum-type and normal-type inflorescences, the segregation ratio in the F-2 populations corresponded to the theoretical ratio of 3:1 for chrysanthemum-type:normal-type inflorescences. We conclude that the genes controlling floral colour and inflorescence type are inherited independently and have different effects. The interaction of these genes revealed new combinations of floral colour and type, which can increase variability in ornamental sunflowers.