Cytogenetic characterization of embryogenic callus and regenerated plants of Pennisetum americanum (L.) K. Schum.

Embryogenic calli were derived from cultured segments of immature inflorescences of Pennisetum americanum (pearl millet). The original explants as well as the embryogenic calli and the plants regenerated via somatic embryogenesis were examined cytogenetically. Embryogenic calli were predominantly diploid (2n=14) after one month and six months in culture (92% and 76%, respectively). Tetraploid and aneuploid cells were observed in the original explant (2.5% and 1.2%) as well as in one (4.0% and 4.0%) and six-month-old calli (10.0% and 14.0%). Plants were regenerated from calli that had been in continuous culture for two, four and six months. Of the 101 regenerants, 100 were diploid and 1 was tetraploid. The tetraploid was an albino as were three of the diploid regenerants. Examination of 30 of the regenerants in meiotic diakinesis, anaphase I, anaphase II and quartet stages revealed no cytogenetic differences between control and regenerated plants. Gel electrophoresis for total protein content and alcohol dehydrogenase and malate dehydrogenase activity also did not reveal any differences between the controls and regenerants. The results of this study show that a slight shift toward aneuploidy and polyploidy may occur in embryogenic cultures, but there also is a strong selection in favor of plant regeneration from cytogenetically normal cells.