Hybrid pearlmillet seed is produced by utilising cytoplasmic genetic male sterility (CMS). Various steps involved in the production of hybrid seed are: Maintenance of parental lines, male sterile line, maintainer and restorer lines. Maintenance of parental lines is referred to as foundation seed production, whereas the hybrid seed production is known as certified seed production.
Maintenance of Male Sterile Lines:
Male sterility is due to cytoplasmic genetic factor. It is maintained by crossing male sterile line (line A) with a male fertile non-pollen restoring maintainer (line B) in an isolated plot. This B line is a sister strain of line A and is essentially similar to line A in genetic constitution except that it carries fertile pollen.
In a crossing field, the usual planting ratio of line A and line B is 4:2. In addition, 4-8 border rows are planted with line B around the field. The seed harvested from line A would be male sterile and is used for hybrid seed production.
The field for producing foundation seed of male sterile line A must be isolated by 1000 m from other pearlmillet field or fields of the same variety not confirming to vertical purity requirements for a certification. Differential blooming dates to modify isolation distances are not permitted.
Maintenance of Maintainer Line:
The seed of maintainer line is produced by sowing B lines in isolated plots by following proper isolation requirements and cultural practices.
Maintenance of Restorer Line:
Seeds of restorer line (line R) is produced by multiplying the seed in an isolated plot having a distance of 1000 m from nearby pearlmillet field having different cultivars or from the same restorer line not conforming to certification standards.
Certified Seed:
Hybrid seed is produced by growing 6 rows of male sterile line A alternated by 2 rows of restorer line R. The 2:6 proportion of male rows (line R) and female rows (line A) can be increased safely to 2:10 depending upon the pollinating vigor of the restorer parent. The seed harvested from the female rows is certified hybrid seed. Requirements for isolation distance are 200 m from field of other verities and 25 m from the field of same variety.
Breeder Seed:
Breeder seed is the seed of highest genetic purity and is produced under the direct supervision of breeder, organising institution or agency. It is the source for the production of foundation and certified seed.
Breeder seed of maintainer (line B), restorer (line R) and synthetics is produced by growing them in isolated plots having a minimum distance of 1000 m from fields of other verities or same variety not conforming to varietal purity requirements for certification. Rouging of off-types, volunteer plants and diseased plants is done for quality seed production. Roughing is done before flowering.