Hybrid Seed Production
In cucurbits hybrid seed production is simplified by ingenious manipulation of sex mechanism and sex expression. Generally, five types of sex expressions viz.
4. Andromonoecious and
5. Androecious are found in cucurbits.
In cucumber the important step is the multiplication of gynoecious seed parent where homozygous gynoecious lines are developed using GA 1500 ppm or silver nitrate 200-300 ppm to induce male flowers. The gynoecious lines are crossed with the monoecious male parents to produce F1 hybrids. These hybrids when grown will be gynoecious requiring pollinizers, whose seeds will be mixed with the hybrid seeds to give a population of 10%. The F1 hybrid seeds are produced by crossing two gynoecious parents preferably by hand pollination. Further, F1 population would be gynoecious and parthenocarpic, completely eliminating the pollinators and seed development in hybrid fruits. These lines when crossed to monoecious in seed lines gives rise to high yielding hybrid seeds.
In another method, male sterile line stocks are maintained. Being a single gene recessive in genetic mechanism, the stocks are maintained under heterozygous condition in isolation, by sibbing male fertile and male sterile plants. If male sterility is incorporated in female parents, the male fertile plants segregating will have to be identified at the time of flowering and pulled out so that male sterile female parent can get pollens from chosen male parent through insects subject to:-
· Male sterility has to be maintained in isolation under heterozygous condition segregating in 1 : 1 ratio.
· The identification of male fertile plants have to be done at flowering stage and pulled out.