Karyotype Instability in Tissue Cultures Derived from the Mesocotyl ofZea MaysSeedlings

Abstract

In the study carried out on tissue cultures obtained from the mesocotyl part of the two diploid strains of Zea mays—SII04 and H-3, the difference in variances of nuclear dimensions between different subcultures in each strain has proved to be highly significant. Nuclei with particular configurations, such as constricted, lobulate, spinous, and those with hair-like projections were frequently observed. Nuclear budding was also frequent. A large number of nuclei contained more than two nucleoli. Variation in chromosome number is remarkable in the strain SII04, the percentage of tetraploids being very high in the 7th and 8th subculture. An actual, though limited, variation in the chromosome number was also observed in the cells of the expiant. In the strain H-3 there is greater genetic stability and a high percentage of diploid cells persists in the 8th subculture. Most of the anaphases observed in the cells of the 8th subculture of the SII04 strain demonstrated abnormalities such as dicentric bridges and/or lagging chromosomes and hypertetraploid cells carrying two dicentric chromosomes were also present. Cells with chromosomal fragments could also be observed in the 7th and 8th subcultures of the SII04 strain.