How to Perpetuate Male-Sterile Line in Onions and Produce Hybrid Seeds for Commercial Crops

a. How can you perpetuate the male-sterile line in onions?

b. Briefly outline the method of producing hybrid seed for the commercial crop. Does the cytoplasmic fertility matter in male fertile inbred lines?

Answer:

Male sterility in onions is controlled by the interaction of a chromosomal allele pair (msms) and a cytoplasmic "sterile" S gene. To perpetuate the male-sterile line in onions, emasculation and pollination are used.

Emasculation involves removing the male reproductive organs (anthers) from the male-sterile plants to prevent self-pollination and maintain the male-sterile trait in subsequent generations. Pollination is then carried out by transferring pollen from male-fertile plants to the emasculated female flowers of the male-sterile plants.

To produce hybrid seeds for commercial crops, the male-sterile line is crossed with male-fertile inbred lines. The male-sterile line serves as the female parent while the male-fertile inbred line provides pollen. This cross-pollination results in hybrid seeds in the F1 generation.

The cytoplasmic fertility (whether fertile or sterile) does not affect the male fertility of the inbred line. The male fertility is determined by the chromosomal allele pair (msms). Therefore, whether the cytoplasm is fertile or sterile does not matter in male fertile inbred lines.