On Ö. Winge and a Prayer: The origins of polyploidy

Abstract

1) Almost all polyploids arise by way of unreduced gametes; other mechanisms occur, but are negligible. 2) The most widespread and common event is (2n+n) reproduction. 3) Triploids so produced frequently yield 4X plants on backcrossing and 6X plants on selfing. 4) Spontaneous polyploids appear repeatedly, but their fate depends on vigor and competitive ability. 5) The polyploids most frequently produced are probably strict autoploids, but they often lack competitive ability and may not become successfully established. 6) Wide crosses occur in nature but not very often; if the hybrid is vigorous, it may yield a stable, fertile polyploid in the second or later generations via unreduced gametes. 7) Wide crosses by way of (2n+n) reproduction are probably more common and successful than the above (6) pathway. 8) The most likely pathway to a successful polyploid in nature involves neither wide crosses nor strict autoploidy but crosses between races, ecotypes and cytotypes within a biological species. 9) The more or less autoploids so produced may generate genuine alloploids by interspecific hybridization at polyploid levels. 10) The classic explanation of alloploidyvia “chromosome doubling” of a sterile diploid interspecific hybrid is misleading in most cases, and this route is probably negligible in the evolution of polyploid systems.