Number of chromosomes and chromosome rearrangement of Norway spruce Picea abies (L.) H. Karst. in the forests of Rilo-Rhodope mountain in Bulgaria

Abstract

Comparative investigations of chromosome numbers and chromosome rearrangements in populations of Norway spruce (Picea abies (L.) H. Karst.) growing in the territory of State Forest Service «Garmen», «Eleshnitsa», «Yakoruda», «Dobrinishte» in Rila-Rhodope mountain region (Bulgaria). Populations are located at the southern border of species range, and protected according to Bern Convention and EC Habitat Directive 92/43. It was found that diploid set of seed progeny of P. abies from the 4 populations studied includes 24 chromosomes (2n = 2x = 24). Mixoploidy (2n = 24, 36; 2n = 24, 48; 2n = 24, 36, 48) was detected in some germinating seeds of all studied populations of P. abies. Metaphase cells of germinating seeds of P. abies from State Forest Service «Garmen» and «Eleshnitsa» contain supernumerary, or B-chromosomes, while the variability of their number and occurrence was observed. In cells of germinating seeds of P. abies from State Forest Service «Yakoruda», «Dobrinishte», B-chromosomes are not revealed. Some chromosome rearrangements such as fragments and ring chromosomes were revealed in metaphase cells of P. abies from populations of «Garmen», «Eleshnitsa» and «Dobrinishte». Probably occurrence of mixoploids, B chromosomes and chromosome rearrangements in P. abies populations growing in Rila-Rhodope mountain region is connected with adaptation of trees to the extreme environmental conditions and such a serious factor that presently forests in the studied region located in the zone of natural radioactivity and in the past, the region of study was subjected to substantial anthropogenic pressure due to uranium extraction industry.

Keywords

• Picea abies
• chromosome numbers
• B-chromosomes
• chromosome rearrangements
• Bulgaria