Occurrence of diploid and polyploid microspores in Sorghum bicolor (Poaceae) is the result of cytomixis

Colchicine is used in this investigation to increase chromosome doubling in Sorghum bicolor Line IS4546. Of a total of 500 plants which were treated, eight of them showed the occurrence of cytomixsis at meiotic stages. No polyploids were found in the treated plants. The results obtained from meiotic studies on control plants showed the 10 bivalents in majority of pollen mother cells at diakinesis and first metaphase. In eight treated plants, occurrence of cytomixis and chromosome migration were observed. Analysis of 230 pollen mother cells at first metaphase stage showed 73.91% haploid (n=10), 10.43% diploid (n=20), 7.82% triploid (n=30), 4.34% tetraploid and 3.47% pentaploid (n=50) number of chromosomes. Pollen diameters showed that the cytomictic cells differed from the normal cells. These results indicate that cytomixis can really be an effective mechanism for the production of polyploid gametes