@seedfork, Most of the statements Bard made are both correct and incorrect.
Bard "However, this doubling isn't always perfect. Sometimes, chromosomes can break, fuse, or rearrange during the conversion process. "
That may be correct as a generalization. However, that is not common, nor is it what is desired when the conversion process is attempted. It is also not unique to the conversion process. That is, it occurs in normal diploid x diploid crosses as well. As far as I know (but I have not searched the original scientific literature on this specific topic) there is no difference between the rates at which those types of "errors" occur in normal reproduction versus successful conversions. Again, it is not wanted in normal conversions. Nor, as far as I know, would the conversion process be used to produce such changes when they were desired. There are other methods that are likely to be used to produce such changes, when they are desired.
Those same "problems" also occur in normal tetraploid x tetraploid crosses. In the case of tetraploid x tetraploid crosses the problems occur much more frequently than in diploid x diploid crosses and are part of the reason why tetraploid crosses are less successful and produce fewer seeds than diploid x diploid crosses.
The potential problems with conversions are not desired when converting a diploid plant to a tetraploid. Nor are they the reason that tetraploid conversions are different from their diploid versions.
Bard "Masking of recessive alleles: Recessive traits present in the diploid parent but masked by dominant alleles can become visible in the tetraploid if all four alleles are recessive."
I would want to see evidence that this has ever been observed in conversions. It requires that a plant that is Aa becomes converted to aaaa. I suspect that it does not occur any more often in the process of converting a diploid to a tetraploid than it does naturally in diploids.
When a diploid is converted to a tetraploid there are fundamental changes that are related to the amount of DNA per cell and both the area of the cells and their volumes. The number of mitochondria and chloroplasts that the cells contain may also affect the characteristics of the cells and the plants.
Bard "While some traits might be lost or altered, many characteristics of the original diploid parent are often retained in the tetraploid offspring. This is because the majority of the genetic material remains intact during the conversion process."
I do not know of any complete conversion of a diploid to tetraploid where a trait of the diploid was lost in the tetraploid. As far as I know all the characteristics of the diploid are retained in the tetraploid. There are fundamental changes that are caused by the amount of DNA in each cell as indicated above.
