coochief - 2/4/2016 20:36

Dmiller, great question and there could be many reasons.   On a legality side of it, any protected or proprietory variety you are not supposed to keep seed for replanting, seed cleaner always asks what variety it is.  I think you can keep the State varietys though for your own use.   

On the agronomy side of things. I've planted Foundation MSU Yellowstone seed to raise for more seed and had the field certified, etc..    What I was shocked to see was that about 1 or 2 in every hundred plants was 6 inches taller and noticibly darker in color. I'm told this was due to some plants retained some of the Genes of their parent variety.    So to try and answer the question, I'm told that many variety's will begin to revert back to their parents in a matter of a couple generations.   So much so, I've been told if somebody were to keep some of the Clearfield variety's for a year or two and spray with Beyond it would actually kill the wheat, this would be highly illegal also.     So depending on how hybrid the variety was it will slowing lose some of its traits it might have been bred for over time.  Old varietys like Promentory or Redwin HRW's can last a long long time though, verses say a new Clearfield hybrid.    Dwarf, and early maturity varieties seem to get taller and slower if keeping seed back for lots of years.  My .02$         These kids nowadays ask some tough questions... lol.  Goodluck!!