Breeding and Seed Production of Ornamental Crops (2+1)

Seed Production Procedure

Seed Production Procedures

A generation production routine has the following components:

1. Parental plant culture
2. Genetic quantity control
3. Pollination management
4. Seed harvest and seed extraction
5. Seed cleaning and conditioning.

Parental plant culture

• Parent plants of most hybrid flowers are raised from seed.
• The seeds are sown in seedling flats or plug trays in a specialized section of the greenhouse serving as the nursery.
• Parents of male sterile lines, for example some impatiens and petunia varieties, are propagated by vegetative cuttings.
• Tissue culture propagated plants are sometimes used for special parent lines of primula and Dianthus. These plants are also raised in the nursery.
• When a hybrid is produced from a cross between a seed and a vegetative raised parent, the time of planting have to be adjusted to ensure synchronization of flowering. Well developed young plants are transplanted into pots and put on benches in the production greenhouse.
• Plant nutrition, disease control and pest management are the most important components of plant culture.

Genetic quantity control

• Genetic purity tests are conducted on stock seed lots. Only seeds of high genetic purity are used in production.
• When the parent plants begin to flower, they are further checked for the presence of off types.
• Rouging is based on plant habit, foliage colour, earliness to flower, flower colour and flower form.
• Breeding companies are responsible for the purity of the stock plants in production contracts.
• All greenhouses used for hybrid seed production are equipped with insect proof screens to prevent accidental pollination by insects form the fields.

F₁ Hybrids of ornamentals

• An F₁ hybrid is produced by crossing between any two genetically different parental lines.
• The first F₁ hybrid was evolved during the 1940s in petunia amongst annuals.
• F₁ hybrids are characterized by increased vigour, uniform in growth habit, dwarf, compact, free flowering, early flowering, huge side tillering, doubleness, gigantic and attractive flower types and resistance towards biotic and abiotic stress.

Steps involved in F₁ hybrid seed production
1. Development of Inbred lines

• Standards open pollinated varieties or wild species are the sources of inbred lines.
• In self pollinated crops, homozygous varieties are used, whereas inbred lines are developed especially for cross pollinated crops.

2. Testing of combining ability

• Repeated test crosses and testing of F₁ hybrids are done to evaluate the parental lines.
• Suitable parental lines to carry out combing ability are developed in the following ways.

Collection of genetically divergent materials
Selection based on performance

1. Comparative evaluation of parents and F₁ crosses for self pollinated crop.
2. Comparison of the yield of inbreds with mean yield of their single cross.

• • Different types of crosses are made to test the combining ability of inbred lines.
• • The top cross and poly cross tests are used to determine Genetic Combining Ability(GCA), single or pair cross for Specific Combining Ability (SCA) and diallel analysis for both the GCA and SCA of male sterile line, respectively, equipped with insect proof screens to prevent accidental pollination by insects from the fields.