Meiotic Behaviour and Nuclear DNA Variation in Some Species of Mammillaria (Cactaceae)

抄録

Meiotic studies of PMCs and 4C DNA content from root tip cells of 8 species of Mammillaria of the family Cactaceae revealed significant interspecific variation in the genome. The haploid chromosome number n= 11 was recorded in M. bocasana, M. boolii, M. grandiflora, M. hahniana, M. occidentalis, M. plumosa, M. rhodantha and M. zeilmanniana. The chiasma frequency significantly varied from 19.42 to 28.80 per nucleus and 1.76 to 2.61 per bivalent. The formation of univalent in some of the cells, spindle anomalies i.e. early or late separation leads to the formation of pentads, sexads or octads instead of tetrads formation in the meiotic telophase II through differential pollen sterility from 9.12 to 32.83% in M. zeilmanniana and M. occidentalis respectively. The 4C DNA amount of root tip cells varied significantly from 18.42 to 27.78 pg in M. bocasana and M. rhodantha, respectively. Significant variation in DNA amount with gross or minor alteration of chiasma frequency leads to differential heritability with genetic drift at species level.