Nuclear DNA content and chiasma behaviour in six species of Gymnocalycium Pfeiff. of the family Cactaceae

Chromosomic Studies in Zephyranthes Citrina Baker (Amaryllidaceae), a Polyploid Ornamental

“…In all populations, the chromosome number of G. quehlianum was 2n=2x = 22, except for one individual of the population at 948 m a.s.l., indicating that a greater number of individuals should be analyzed in each population in order to explore whether the different chromosome numbers are associated with the altitudinal gradient. The chromosome numbers reported here coincide with meiotic studies that included the determination of pollen stem cells (Das and Das, 1998). Furthermore, no significant differences in the cytogenetic variables were detected among populations.…”

“…The cytogenetic data available for G. quehlianum indicate that it is diploid (2n=22) and its DNA content is 2C=6.46 pg (Das and Das, 1998). Ploidy level is an important characteristic that may be affecting speciation and patterns of species diversity.…”

Cytophotometric Estimation of 4C DNA Content and Chromosome Analysis in Four Species of Astrophytum Lem. of the Family Cactaceae.

“…The estimated 4C DNA values were reported for the first time in the 4 studied species of Astrophytum. Significant differences of 4C DNA were recorded at interspecific level; such variations were noticed in other groups of cactus like Mammillaria (Das et al 1997, 1998a, 1999a, b, d, Mohanty et al 1996, 1997a; Melocactus (Das et al 1998b, c); Gymnocalycium (Das and Das 1998) and Ferocactus (Das et al 1999c). The constancy in the DNA amount at the species level in repeated experiments revealed a stable 4C DNA content in each species.…”

Interspecific variations in the chiasma frequencyand nuclear DNA content in some species of Ferocactus (Cactaceae)

“…The chiasma frequency, showed a high correlation with 4C DNA content (0.812). Nuclear DNA values and chiasma frequency in these species of Ferocactus are reported for the first time, although such interspecific variations were reported earlier in several other species (DAS and DAS 1998;DAS et al 1999). The vari ability in the stable DNA amount might be at tributed to the loss or addition of many repeats in the microand macro-environment during evolution of new species (PRICE 1976).…”

“…They grow to 3 m high in full sun, in rocky places and grassy pastures as well (HEY-WOOD 1985). Chromosome analysis reported by earlier worker showed n=11 bivalents (REMSKI 1954); however, no report on meiotic and cytophotometric estimation of nuclear DNA con tent in Ferocactus was available except our ear lier communication on the karyotype analysis and nuclear DNA content (DAS et al 1999). The present report deals with meiotic chromosome number, chiasma behaviour and DNA content in 10 species of Ferocactus to ascertain the selective advantage of these values in the de velopment of new species.…”