3.The character can stable heredity at generation D 3-D 4. This method can reduce years of the breeding, so this experiment is very important to the theory and practice of flax breeding.
5.With the improvement of cultivation practice and directional breeding of new crop varieties,the harvest index of cereal crops has enhanced universally to 0.4～0.5 from about 0.3,and even to 0.6.HI has higher hereditary capaciuy,but is influenced by agronomical practice.
6.Related species that are not geographically isolated, and which could interbreed but in practice do not because of differences in behavior, breeding season, etc., are called sympatric species.
