Plant Breeding

Gain Skills for the Nursery and Plant Breeding Industry

• Learn the principles and practices of plant breeding.
• Indulge a passion, start a business, work in plant development
• Expand your career possibilities in the nursery and broader horticulture industry

Plant breeding is a bigger industry than most people realise. In some places, earnings from plant breeding rights can equal or exceed earnings from actually producing plants. Today's nurseryman needs to understand plant breeding and selection; and to this end, this course is a very valuable and unique course for anyone working in the modern industry.

Lesson Structure

There are 7 lessons in this course:

1. The Scope and Nature of the Plant Breeding Industry
2. Introduction to Genetics
3. Gamete Production, Pollination and Fertilisation in Plants
4. Mono Hybrid and Dihybrid Inheritance in Plants
5. Systematic Botany and Floral Structures
6. Practical Plant Breeding Techniques
7. Current Developments in Plant Genetics

Aims

• Describe the commercial and scientific nature of the modern plant breeding industry, on a global basis
• Describe the structure and function of genetic material
• Describe gamete production in plants.
• Explain the results of mono hybrid and dihybrid inheritance in plants.
• Investigate the role of systematic botany in horticulture.
• Explain a variety of different plant breeding techniques
• Review current developments in plant breeding.

Plant Breeding Tips

The essential aspects of most breeding programs are:

1. Selection of genetically variable individuals or families within a base population.
2. Using the selected material to create new populations for use either as potential commercial varieties or as the basis for a new cycle of selection.

Before starting a breeding program, it is essential to know the plant’s pollination requirements – whether it is self or cross pollinated – and how it behaves when it is inbred or crossbred.

BREEDING SELF-POLLINATED CROPS
The genetic effect of continued self fertilisation in self-pollinated plants is to reveal the dominant and recessive genes. As Mendel’s experiments show, heterozygosity is reduced by one half in each generation, so that after six or seven generations of selfing, a population will consist almost entirely of equal numbers of homozygotes. In this way, selection of characters by continued selfing results in pure lines – these plants are said to be ‘pure breeding’ or breeding ‘true to type’.

The following methods are used to breed self-pollinated crops.

Pure-line Breeding
In pure-line breeding (also known as ‘single plant selection’) the new variety is made of the progeny of a single pure line. It involves three steps:
1. Selecting a large number of superior individuals from a genetically variable population.
2. Raising the self progeny of each of these over several years, preferably in different environments. Unsuitable lines are eliminated in each generation. When the breeder can no longer select superior lines by observation only, the third step is commenced.
3. Replicating the trials to compare the remaining selections. This is done over several seasons (at least three years) to compare them with each other and with existing commercial varieties.

Mass Selection
In mass selection the progeny of many pure lines are used to form the new variety. Unlike pure-line selection where the derived type consists of a single pure line, in mass selection the majority of selected lines are likely to be retained.

It is not as rigorous as pure-line breeding – obviously inferior plants are destroyed before flowering but overall many lines are kept and contribute to the genetic base. This gives the advantage of retaining the best features of an original variety and avoids the extensive testing required in step 3 of pure-line breeding.

Pedigree Breeding
This is the most widely used method of breeding in self-pollinated plants. Superior types are selected in successive segregating generations (as in pure-line breeding) and a record is kept of all parent-progeny relationships. It starts with the crossing of two varieties which complement each other with respect to one or more desirable characters. In the F2 generation a single plant selection is made of the individuals the breeder thinks will produce the best progeny. In the F3 and F4 generations, many loci become homozygous and family characteristics begin to appear. By the F5 and F6 generations, most families are homozygous at most loci; hence selection with families is no longer very effective, only between them.

Its main advantage is that the plant breeder is able to exercise his/her skill in selecting plants to a greater degree than other self-pollinating breeding methods. A disadvantage is the limitation it has on the amount of material one breeder can handle.