Male Sterility

Male sterility

      

When the pollen grains are non-functional, they are said to be sterile. There are 3 types of male sterility-

1) Genetic or genic male sterility-

In these cases, one or more nuclear genes are responsible for the sterility of pollen grains. This type of male sterility always show Mendalian ratio.

               Female parent                                           Male parent

                   ms/ms                                 X                    Ms/Ms

           (male sterile)                              $               (male fertile )

       F1                                               Ms/ms

                                                               ¯

        F2                                              3:1                                                      

                                         Male fertile: Male sterile

             

      

 2) Cytoplasmic male sterility-

These plants have normal nuclear set up, but it may contain certain mitochondrial genes (eg Maize) which hamper the wall formation in pollen grains, by faulty enzymes. So the pollen grains formed in this manner are sterile. The pollen grains abort at mononucleate, binucleate or trinucleate stage.

                 

                   Female parent                 X                 Male parent                  

                   (Male sterile)                   ¯                  (Male fertile)

                               F1                                     Male sterile

                                                                           100%

   

3) Cytoplasmic- Genetic male sterility-

In this type, the male sterility is due to both cytoplasmic (and extra chromosomal) and nuclear genes. Neither the genetic factor nor the cytoplasmic factors alone is able to cause male sterility.

            

Here the gene (ms) stands for male sterility and (Ms) for fertility, the gene (Ms) is dominant over the (ms). A plant will be male sterile only if it carries sterile cytoplasm(S) and when both genes are also (ms/ms). If any of these genes is dominant, then the plant will be male fertile.