Figure 3.

The distribution of plants with different chromosome numbers at four successive segregating generations, from pentaploid F₁ to F₄. (A) The segregation of F₁ plants with different chromosome numbers and seed set. In the F₁ generation, the number of seeds produced from each category of plants with a different chromosome number is also presented. Self-pollinated seeds from F₁ plants with 44 or 45 chromosomes were selected (as indicated by the arrows on the bottom) to produce offspring. (B) The segregation of plants with different chromosome numbers at the F₂ generation, which originated separately from F₁ plants with 44 or 45 chromosomes. Plants with 36 to 38 chromosomes were selected to produce offspring. (C) The segregation of the plants with different chromosome number in the F₃ generation, 50 to 80% of plants derived from F₂ plants with 38, 37, or 36 chromosomes were identified as having 36 chromosomes; only plants with 36 chromosomes were selected as new-type B. juncea. (D) The majority of the plants in the F₄ generation inherited 36 chromosomes. The arrows indicating the selected plants were filled with colors and grains that were the same as the columns in the picture in the next generation. The cytological photographs illustrate the correct chromosome numbers of 45, 36, 36, and 36 in the pentaploids, target F₂ plants, and new-type B. juncea (F₃ and F₄), respectively.