Inheritance of internode length, plant form, and annual habit in a cross of cabbage and broccoli (Brassica oleracea var. capitata L. and var. italica Plenck.)

Summary

When an inbred line of cabbage, Brassica oleracea L. var. capitata L., was crossed with an inbred line of broccoli B. oleraceae var. italica, the F₁ progeny were vigorous late annuals. All F₁ × broccoli backcross plants and 92% of the 3260 F₂ plants were annuals, while 40% of the F₁ × cabbage backcross plants were biennials. Annual habit is thus dominant and controlled by more than a single gene. Number of days to bud appearance in annuals varied continuously, and was primarily additive in inheritance. F₁ data suggested partial dominance for lateness but this was not supported by the F₂. Internode length was also continuous in distribution and primarily additive in inheritance, but with some dominance for short internodes in the F₁. Cabbage head forming ability was recessive and multigenic, with 2% of the F₂ plants forming heads, of which none were of commercial type and about half bolted as annuals. There was a significant chi square association between biennial habit and tendency for cabbage head formation. Clasping habit of terminal leaves was recessive to open leaves, multigenic, and associated with both cabbage heading and biennial habit.