Polyploid gamete formation in diploidAvena hybrids

Summary

Three methods by which polyploid gametes were formed in segregates of a diploidAvena species hybrid have been described in this paper. They may be briefly outlined as follows:

• 1. (a) First and most frequently from a giant pollen mother cell, which at the first meiotic division had a giant nucleus containing 14, 21, 28 or more bivalents, according to the number of nuclei which had fused to form the giant nucleus.

• (b) Secondly, from a normal pollen mother cell in which, due to the absence of a dividing cell wall, fusion of the two M. II plates took place so that ultimately a dyad pollen grain was formed, the nucleus of each cell having 14 chromosomes.

• (c) Thirdly, from a normal pollen mother cell, in which there was a complete failure of cell wall development so that the whole pollen mother cell, containing 4 nuclei, each with 7 chromosomes, became a giant pollen grain. In this case the two meiotic divisions have proceeded normally.

• 2. Absence of cell wall development is an important factor of polyploid gamete formation in all the methods described.

• 3. While the polyploid gametes appear to be healthy and viable, no evidence is yet available to show whether they are functional or not.

• 4. The possible evolutionary significance and economic value within the genusAvena of such polyploid gametes, if functional, is discussed.