Analysis of Genetic Variability in Long-term Callus Cultures and Regenerated Plants of Maize

Abstract

Zea mays ssp. mays cv. Colorado Klein organogenic calli were initiated from 11 daysold embryos on basic medium containing 2.25 μM 2, 4-D. The callus originated from one of the embryos was subcultured every month to fresh medium supplemented with 4.5 or 9 μM 2, 4-D, for 84months. The first chromosomal abnormalities appeared after 17 months of culture : 70% of regenerated plants were normal, 20% aneuploid and the remaining 10% were tetraploid. Thereafter chromosomal aberrations increased. Most (95%) of the plants regenerated after 32 months had one extra chromosome, and meiotic analysis of regenerants showed deficiencies, duplications, inversions, translocations and ring chromosomes. Chromosome number of cells from 60 months old callus ranged from 2n=18 to 2n=23, but 90% of regenerated plants had 2n=21 and the remaining 10% had 2n=20. Plants regenerated from 64 to 84 months old callus were sterile. Also, phenotypic alterations were observed in plants regenerated from 32 months and older calli. Although original maize plants are yellow flint, 75% of R0 ears showed white flint kernels and their progeny exhibited yellow flint, white flint, white dent and white sugary caryopses.