Genetic system and results
Potato breeding is characterized by:
- most potato breeding programmes are implemented at the tetraploid level
- the potato is a vegetatively multiplied crop and is heterozygous
- environmental factors greatly affect the phenotypic variation
TETRAPLOIDS AND DIPLOIDS-------PHENOTYPIC VARIATION
Traits controlled by dominant genes
Breeding for traits based on dominant genes is relatively easy:
- the frequency of appearance in progenies is high
- presence of the gene results in a complete protection/ or no plant
reaction against a disease ( + ) and no protection/ and a clear reaction of the plant ( - ) under the absence of the gene.
This clear symptom expression facilitates selection
Traits controlled by recessive genes and polygenic systems
Breeding for traits based on polygenic genetic system is a long process.
The reasons are:
- a low proportion of the crossing progeny has the desired characteristics.
- the characteristic to be introduced, is diluted when crosses are made with parental material
that does not possess genes for this trait
- selection of genotypes is difficult because the large effect of the environment on the
phenotype
- plants react intermediately ( ± ) to polygenic systems and selection is difficult.
Expected progress in breeding
Progress made in breeding depends on the numbers and the nature of the characteristics to be introduced.
EXPECTED PROGRESS IN BREEDING