结球白菜核不育复等位基因转育模式V 1.杂交 S(msms)×N(MsMs) 2.反回交 N(MsMs)×s(Msms) 3.自交 N(MsMs) -N(Msms) 1⑧ ⊕ (育性不分离) (育性分离) 4.测交N(MsMs)S(msms)×N(msms)S(msms)×N(Msms)S(msms)×N(MsMs) ⑧ 5.鉴定 (获得B系) 海汰 S(msms)N(msms)S(msms)S(Msms)S(Msms) 不育系(A系)保持系(B系) 人工合成保持系示意图 2.Functional Male Sterility In some instances although the plant produces normal amount of viable pollen, the pollen is not released because of a defective dehiscence mechanism.The anthers do not open and shed the pollen.The various aspects of use of functional male sterility have been more widely investigated in tomato,where it has been reported that non-dehiscence is highly sensitive to environment.For this reason functional male sterility has seldom been used in commercial FI hybrid seed production of tomato. 3.Chemical Induction of Male Sterility A chemical,i.e.,a chemical gametocide,having the ability to induce pollen sterility or check pollen shed may be suitably employed in hybrid seed production. Criteria for a good gametocide 1)Once standardized,it should give consistent,reproducible results.It should cause pollen abortion only.Ovule fertility should not be impaired in any way. 2)It should be free from any mutagenic effect. 3)The method of treatment should be simple and easy to adopt in the field. 4)It should be economic. 4.Limitations of chemical hybridizing agents (CHAs) The available gametocides for hybrid seed production have not been put to extensive practical use,primarily for three reasons: 1)pollen abortion is incomplete and erratic,treatment is effective for short periods and at a particular stage in plant development and hence needs to be repeated; 2)female fertility is somewhat adversely affected,and 3)cost is relatively high. 1515 结球白菜核不育复等位基因转育模式Ⅴ 人工合成保持系示意图 2. Functional Male Sterility In some instances although the plant produces normal amount of viable pollen, the pollen is not released because of a defective dehiscence mechanism. The anthers do not open and shed the pollen. The various aspects of use of functional male sterility have been more widely investigated in tomato, where it has been reported that non-dehiscence is highly sensitive to environment. For this reason functional male sterility has seldom been used in commercial F1 hybrid seed production of tomato. 3.Chemical Induction of Male Sterility A chemical, i.e., a chemical gametocide, having the ability to induce pollen sterility or check pollen shed may be suitably employed in hybrid seed production. Criteria for a good gametocide 1) Once standardized, it should give consistent, reproducible results. It should cause pollen abortion only. Ovule fertility should not be impaired in any way. 2) It should be free from any mutagenic effect. 3) The method of treatment should be simple and easy to adopt in the field. 4) It should be economic. 4. Limitations of chemical hybridizing agents (CHAs) The available gametocides for hybrid seed production have not been put to extensive practical use, primarily for three reasons: 1) pollen abortion is incomplete and erratic, treatment is effective for short periods and at a particular stage in plant development and hence needs to be repeated; 2) female fertility is somewhat adversely affected, and 3) cost is relatively high