Objective   The very complex genetic characteristics at heading stage that dictate the adaptability of a rice variety to ecological zones were studied.

  Method   Using Huazhan as male parent, populations of 6 generations (i.e., P₁, P₂, F₁, F₂, BC_1-1, and BC_1-2) of combination rice hybrids, Tianyou Huazhan (TH), Hengfengyou Huazhan (HH), and Wufengyou Huazhan (WH), were constructed. Genetic analysis on the heredity of plant height was performed using the "main gene+polygene hybrid genetic model" on the populations.

  Result  MX1-AD-ADI was found to be the best fit genetic model for the heading of all 3 hybrids. On F₂, the main genetic heritability of TH was 10.13%, that of HH 12.64%, and that of WH 13.65%; and, the polygenic heritability of TH was 88.45%, that of HH 85.94%, and that of WH 83.66%. For the BC_1-1 population, the main gene heritability ranged from 15.16% to 23.66%, and the polygene from 65.33% to 69.75%. For the two populations, the genetic patterns at the heading stage were mainly controlled by the polygenes. But the heading of the 3 backcrossing BC_1-2 populations with the maintainer as recurrent parent were affected by both the main genes and polygenes with the former exerting a heritability between 42.03% and 47.78 %, and the latter between 45.17% and 50.77%.

  Conclusion   Rice heading was highly complicatedly controlled by multiple genes. In breeding, selection of heading period would, therefore, require a thorough analysis beforehand on the genetic characteristics of the specific target population.