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 colchicine solutions on mitotic index was investigated in embryogenic suspensions and in seedling root tips of Picea mariana. Hydroxyurea treatment and 0.6 per cent colchicine 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 m-type having median centromeres and two pairs are metacentric or M-type. © The Genetical Society of Great Britain.