Cytogenetic analysis of regenerants from Nicotiana tabacum L. cv Romero: effect of leaf age.
1987
Beltran Z.P. | Mercado M.S. | Javier E.L.
The study was conducted to determine the chromosome number and behavior of regenerants from callus obtained from the second, fourth and sixth leaves of a tobacco haploid (Nicotiana tabacum L. cv Romero) derived through anther culture. Thirty-three regenerants from the second leaf, 35 from the fourth and 32 from the sixth were evaluated. All regenerants were haploid (n = 24) except 2 which were diploids (2n = 48). One diploid regenerant had either 24 bivalents or 48 univalents in metaphase 1 cells. It also had 1 to 12 microchromosomes. The other diploid exhibited 24 bivalents at metaphase 1. Chromosome associations other than the regular homologous pairing of diploid tobacco were found in many regenerants the frequency of non-aligned chromosomes at metaphase 1 and 2, laggards and bridges at anaphase 1 and 2, and laggards at telophase 1 and 2 among regenerants increased with increasing leaf age of explants. This could be due to greater chromosomal instability in older explant leaf sources than in younger ones.
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