Inheritance of cabbage head formation in crosses of cabbage × ornamental cabbage and cabbage × kale

We investigated the inheritance of head formation in Brassica oleracea by using two crosses, cabbage × ornamental cabbage and cabbage × kale. The degree of head formation (DHF) was classified into nine grades ranging from non‐heading to full heading. DHF in the two F₂ populations showed a continuous distribution. The variance of F₃ offspring selected for full heading or non‐heading was large. The DHF distributions in the F₃ offspring selected for moderate heading or randomly selected F₃ populations were similar to those of the respective F₂ populations, but had smaller average values and variance. However, the realized heritability in F₃ offspring was similar in full‐heading and non‐heading selections. Our findings suggest that head formation is a quantitative trait controlled additively with low dominance effects. In comparisons of leaf developmental patterns among the parents, only cabbage showed a change in leaf shape becoming wider because of the shorter petiole length with increasing leaf position. These findings suggest that cabbage acquired the developmental changes in leaves required to form a head during the process of domestication.