Hybrid Maize Seed Production: A Continuous and Essential Process for Agricultural Development

The development of new maize hybrids, variety maintenance, and seed production form a continuous and indispensable process for successful agriculture. A key factor in the rapid adoption of newly developed hybrids into mass production is the efficient organization of their seed multiplication.

The Essence of Seed Production

Seed production is a scientific discipline focused on maintaining seed identity while ensuring:

·      High genetic purity

·      Excellent sowing, yield, and biological qualities

·      Consistency across different multiplication stages until the required volumes are achieved.

Seed production is closely linked to breeding and serves as its natural extension. It enables the realization of breeding achievements (new hybrids) and facilitates variety replacement and renewal.

Stages of Hybrid Maize Seed Production

1. Breeding Nursery (Variety Maintenance)

·      Parental lines of the institute’s hybrids are multiplied here.

·      To ensure genetic purity and identity, controlled pollination is conducted under isolation.

·      This method allows multiple lines to be multiplied in a small area while preventing biological contamination.

2. Pre-Basic Seed Multiplication

·      Pre-basic seed plots are established at least 200 m away from other maize fields to prevent cross-pollination.

·      Seeds from the breeding nursery (isolated multiplication) are used for sowing.

·      Negative selection is applied before flowering to remove:

·      Atypical plants

·      Diseased or stunted plants

·      Only typical, healthy ears are harvested, dried, and shelled after storage inspection.

3. Basic Seed Production

·      Achieved by multiplying pre-basic seeds under open pollination in isolated plots.

·      The same selection and maintenance methods as in pre-basic seed production are applied.

4. Hybrid Seed Production

·      Hybrid plots are sown on isolated fields, spatially separated from other maize crops.

·      Controlled cross-pollination is performed between parental lines, ensuring the female parent is pollinated only by the male parent.

Methods for Producing CMS-Based Hybrid Seeds

1. Fertile Basis Method

·      100% manual detasseling of the female parent.

·      Applied when no sterile female analog is available.

2. Mixed Method (30% Manual Detasseling)

·      Used when:

A male-sterile female analog is available.

A sterility maintainer is present.

The male parent lacks fertility-restoring genes.

·      1/3 of female rows are sown with a fertile analog and detasseled.

·      All female rows are harvested together, resulting in a homogeneous mix of fertile and sterile hybrid seeds.

3. Fertility Restoration Method

·      Applied when:

A sterile female parent is used.

The male parent is a homozygous fertility restorer.

·      CMS-based seed production with fertility restoration is the most cost-effective and high-quality method.

Innovative Yield-Boosting Technology: The "PLUS" System

A novel agronomic solution to increase hybrid maize yields without additional costs for producers:

·      Strip or mixed sowing of several hybrids with identical maturity, following a mixing scheme.

·      Higher productivity is achieved through:

Xenia effect (heterogeneous pollination benefits).

Increased yield from plants with sterile tassels.

Conclusion

Hybrid maize seed production is a scientifically rigorous process ensuring genetic purity, yield stability, and adaptability. Through advanced breeding, controlled pollination, and innovative agronomic practices, the Maize Research Institute – Knezha continues to enhance maize productivity and sustainability in Bulgarian agriculture.