Production of Hybrid Sunflower Seed
Principle of Hybrid Seed Production:
Hybrid sunflower is produced by using cytoplasmic male sterility and genetic fertility restoration system. The male sterile line (A line) contains sterile cytoplasm and recessive genes for fertility restoration. This is maintained by a male fertile counterpart (Line B) which also contains recessive genes, but has fertile cytoplasm.
For production of hybrid seed male sterile line ( A line) is crossed with a fertility restoring line ( R line) which has the dominant genes for fertility restoration, but may have either sterile or fertile cytoplasm. The restorer line ( R line) should nick well with A line to produce F1 hybrid seed.
1. Production of Male-Sterile Line (A line) Seed:
Land Requirements:
Land requirements are the same as for open – pollinated varieties.
Isolation Requirements:
Seed fields must be isolated form other sunflower fields, same line increase fields not conforming to varietal purity requirements of certification and wild sunflower spp. at least by 600 meters.
Planting Ratio:
The proportion of female line (A line) and male line (B line) should be 3:1. However, the first two border rows on either side may be sown with the male line (B line) seed to ensure enough pollen supply.
Seed Rate:
A line: 7.5 kg/ha and
B line: 2.5 kg/ha
Other cultural practices are the same as described for open pollinated varieties.
Roguing:
The male-fertile plants in the female parent lines should be removed each day during nbchm the entire flowering period. This is best done in the morning hours before the bees have removed the pollen. Roguing for off types should be done in the similar manner as described for open pollinated varieties.
Supplementary Pollination:
For supplementary pollination (Hand Pollination) the palm is first gently rubbed on the male parent flowers and then on the stigmas of the female line to transfer the pollen.
Harvesting:
The male parent rows should be harvested prior to harvest of female rows to avoid contamination. No male parent heads should be left intermingled with the female parent rows. Other aspects of harvesting are similar as described earlier for open pollinated varieties.
2. Production of Maintainer line (B line) and Restorer line (R line) seed:
The seed is produced in an isolated field in the manner similar to that described for open pollinated varieties. The isolation requirements however are higher and shall be same as given for production of “A” line seed above.
3. Production of Hybrid Sunflower Seed:
Land Requirements:
Land requirements are same as for open pollinated varieties.
Isolation Requirements:
Seed fields must be isolated at least by 400 meters from the fields of other varieties, commercial hybrid of the same variety, fields of same hybrid seed production not conforming to variety purity requirements of certification.
Planting Ratio:
The proportion of female parent ( A line) : Male line ( R line) should be kept at 3:1 however, the first two border rows on either side may be sown with the male parent seed to supply enough pollen.
Seed Rate:
A line : 7.5 kg per ha
R line 2.5 kg per ha.
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