I am using some of these techniques to breed for northern fruit. The fruit is slow to develope and are often full of genes that are difficult to recover being recessive. Patience is required- so do not see this as a magic bullet.
It is often useful to use artificial polyploids in breeding, particularly when we want to breed diploids with tetraploids while avoiding the triploid intermediates. However, “the frequency of chiasmata per chromosome is always reduced in a tetraploid owing to the larger nucleus and the slower pairing” (Darlington: The Evolution of Genetic Systems, p. 154).
In other words, if the diploids carry undesired gene linkages, it is a good idea to break the linkages at the diploid level. Once these are brought into tetraploids, they will be more difficult to correct because of reduced crossing-over.
Hi Karl Yes I agree with your quote is correct on reduced crossovers is true but I am only trying to say that in an autotetraploid recovering genes from AAaa x AAaa is I in 36. In diploids Aa x Aa is 1 in 4. For small scale breeders this is significant.
Allotetraoids on the other a barrel of monkeys. I use them like Sears in the fifties and more to move genes from tetraploid to diploids. I know usually it is done in the opposite direction.
Johannes.
Johannes,
Snatching genes from polyploids to enrich the diploid lines is an excellent plan. Percy Wright made just such a suggestion:
Why does someone not undertake to put pollen of ‘Persian Yellow’ (> R. foetida persiana> ) on one of the nearest-to-yellow teas? The hybrid so produced should make a proportion of haploid pollen cells. These, fertilizing the teas again, should create a new race of roses in which it should be somewhat easier to intensify the yellow color than in our existing hybrid teas. Also, it should be easier to avoid inheriting the gene or genes for susceptibility to blackspot which come down from ‘Persian Yellow.’
http://bulbnrose.x10.mx/Roses/breeding/Wright/Wright_chromosomes.html
It also would be desirable to bring the scent foliage of the Sweet Briar (Rosa rubiginosa) and the red leaves of R. rubrifolia into diploids.
I once raised a mossy seedling from ‘Perle d’Or’ pollinated by a Moss rose, but did not continue the work to a useful conclusion.
Karl