Karyotype analysis and optimization of mitotic index in Picea mariana (black spruce) preparations from seedling root tips and embryogenic cultures

Abstract

The effect of hydroxyurea and coichicine solutions on mitotic index was investigated in embryogenic suspensions and in seedling root tips of Picea mariana. Hydroxyurea treatment and 0.6 per cent coichicine solution significantly increased the quantity of mitotic cells which were mostly in the metaphase stage. The highest mitotic index was observed in cells of embryogenic suspensions. The embryogenic lines were cytologically stable and their utilization for karyotype studies and technique development holds great potential. The arm ratios and relative chromosome length values showed the same trends between embryogenic cultures and seedling root tips and among the five black spruce populations studied. This study shows that the black spruce karyotype is asymmetric and semi-advanced, as in Larix and Abies. Three pairs of chromosomes are of the sm-type with submedian centromeres. One pair is median-submedian (msm), six pairs are rn-type having median centromeres and two pairs are metacentric or M-type.

Karyotype evolution in the Pinaceae: implication with molecular phylogeny

“…This model contemplates that structural characteristics of the genome restrict the posi- tion and the number of breaks that could occur and the type of rearrangements that could form. Even though both mechanisms would have similar results, most available molecular and chromosome data favor the position that chromosomal mutations are not only nonrandom but are constrained by chromosome structure (i.e., to the type of change that can be produced) (Peters 1982;Shaw et al 1983;Narayan 1998;King 1993;Seijo and Fernandez 2003). The pattern of evolution at the molecular and subchromosomal levels suggests that, in general, species within this group and other pines evolved in a concerted fashion, maintaining the general karyotype morphology.…”

“…In recent years, modified chromosome spread techniques have been developed that provide a large number of high quality metaphase cells Klimaszewska 1994, 1995;Nkongolo 1996Nkongolo , 1999IslamFaridi et al 2007;Mehes-Smith et al 2011). Consistency in the detection of the locations of secondary constrictions has been improved (see Fig.…”

“…The lack of accuracy in conifer karyotyping in previous studies was ascribed mostly to the use of inappropriate techniques resulting in distorted and long chromosomes and to low mitotic indices (Nkongolo and Klimaszewska 1994;Nkongolo and Klimaszewska 1995;Nkongolo 1996;Nkongolo 1999;Islam-Faridi et al 2007). In recent years, modified chromosome spread techniques have been developed that provide a large number of high quality metaphase cells Klimaszewska 1994, 1995;Nkongolo 1996Nkongolo , 1999IslamFaridi et al 2007;Mehes-Smith et al 2011).…”

“…The chromosomes in this family are large in size (Ն10 m). The karyotypes can range from "least derived" (ancestral) as in Pinus (Saylor 1961(Saylor , 1983, with median centromeres and small differences in relative size; to "moderately derived" as in Abies (Mergen and Burley 1964) and Picea (Yuhong and Maoxue 1985;Nkongolo 1996), with a number of submetacentric chromosomes; and to "derived" as in Larix (Simak 1964a(Simak , 1964b(Simak , 1966Nkongolo and Klimaszewska 1995), Pseudolarix menziesii, and Pseudolarix amabilis. The karyology of Pinus spp.…”

Cryopreservation of Embryogenic Cultures of Conifers and Its Application to Clonal Forestry

“…Similarly, Isabel et al (1993) found no variation in RAPD profiles in somatic embryos from three black spruce lines. Nkongolo and Klimaszewska (1994) and Nkongolo (1995) detected no aneuploidy nor any other abnormalities in black, red and white spruce lines after extended culture. Similar findings were made for 4 lines from 2 larch species after 5 years of culture (Nkongolo and Klimaszewska 1995).…”