Polyspermy versus unreduced male gametes as the origin of nonaploids (9x) common wheat plants

SUMMARY

Four nonaploid plants (2n = 9x = 63) of common wheat found amongst approximately 9000 cytologically analyzed plants, constitute the subject of this article. Two nonaploid plants derived from hand-crosses and since they showed telocentrics in their karyotypes were exhaustively analyzed to establish their probable origin. One of them (2n = 62+ 1t) seems likely to be the result of a fertilization of the oosphere by two normal male gametes (polyspermy) instead of a single unreduced male gamete. In the second case (2n = 62 + 2t), similar conclusion could be reached, again fertilization by two different normal male gametes seems the most likely explanation, given the simultaneous occurrence of two very uncommon phenomena in wheat, i.e. twin (2n = 41 + 2t) and nonaploid (2n = 62 + 2t) plants production. Two additional cases (2n = 63) derived by selfing euploid plants were recorded only to establish the frequency of spontaneous nonaploidy.

Key words:

• Triticum aestivum
• nonaploid common wheat
• unreduced gametes
• polyspermy
• polyploids origin