Inheritance of Annual Flowering in Brassica oleracea

Abstract Segregation for annual vs. biennial flowering habit was observed in F 2 progenies from crosses of early and late-maturing broccoli ( Brassica oleracea L. Italica Group) inbred lines with cabbage ( B. oleracea L. Capitata Group), kohlrabi ( B. oleracea L. Gongyloides Group), collards ( B. oleracea L. Acephala Group), kale ( B. oleracea L. Acephala Group), and brussels sprouts ( B. oleracea L. Gemmifera Group). F, progenies were usually completely annual. F 2 progenies from crosses involving late broccoli contained two to five times as many biennials as F 2 progenies from early broccoli crosses. Maturity factors carried by the biennial parents also appeared to affect expression of flowering habit. Annual habit is dominant over biennial and is controlled by several major genes with a strong effect of modifiers from both the annual and biennial parent. Time of heading of annual plants in F 2 progenies appeared to be controlled by quantitative, mainly additive, factors. Distribution of heading dates for the F 1 and annual broccoli parents showed a large environmental or cultural effect. It appears that the biennial parents, especially brussels sprouts and collards, contributed strong factors for late maturity.