Question

why is emasculated of a bisexual flower necessary in crop improvement programme

Answer 1

Crop improvement programme involves crossing different varieties of plants to produce the new one with improved features. This cross hybridization involves transfer of pollen from flower of one plant to the stigma of flower of another plant variety.

If the female plant (plant that contributes female gametes (egg cells) for obtaining hybrid seed) is bisexual, then emasculation is done to prevent self pollination.
Emasculation is the process of removing pollen grains from the flowers. Then the emasculated flowers are bagged to avoid landing of any unwanted pollen. Pollen grains from the dehisced anthers of the desired male plant are then shed on the stigma of female flowers. This process is called cross pollination. After, the successful fertilization of male and female gametes, hybrid seeds are obtained.