GENERAL ASPECTS OF GENETICS IN PLANT PROPAGATION

1. The reproduction of typical parent characters after generative as well as vegetative propagation, and
2. the genetic potential for the character "propagation rate"

I would like to discuss first the mentioned "Reproduction of parent characters". What is a reproduction of typical parent characters; is this given when only identical copies of a mother line are produced, or is reproduction also achieved, when smaller or larger differences, i.e. genetic variants, are found in progenies? For example: flower colour offspring in sown Gallistephus or changed flower colours in grafted cut roses? Genetic variants in this sense are reproducable alteration and not modifications which will normally disappear at the latest after a next propagation cycle.

The tolerated genetic variability in a propagation generation is either fixed through an official testing and description of the variety characters or, in most of the ornamentals, by the growers, distributors or consumers. Thus, reproduction of typical parent characters is a variable factor.

What are the reasons for genetic variability in plant progenies and if undesired, how to reduce it?

As announced, I can refer only to general aspects and not give now detailed information on specific breeding strategies used. But please follow my proposal and divide the answered question into the subunits A.1. to A.6., where A.1. includes generative propagated and A.2. vegetatively propagated plants, A.3. to A.5. a generative and vegetative propagation and finally A.6. the Apomixis (Table 1).

Among the generative propagated plants (Table 2) in the group of self pollinating ones, undesired genetic variability in progenies will result from genetic inhomogenity of the parent. If more than one parent genotype is included in a cultivar, also variability between homozygous plants can be the reason for an undesired offspring. Nevertheless, spontaneous mutations may occur, resulting in offspring in subsequent generations. How to overcome this inhomogenety? This is possible through: Elimination of undesired genotypes before harvesting, separation of populations into single plant

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