First report on chromosome number and genome size of rare endemic birch Betula klokovii Zaverucha from Ukraine

Abstract

This study presents the first report on chromosome number and genome size estimate for rare endemic birch species Betula klokovii Zaverucha from Ukraine. Karyological analysis of metaphases revealed a total of 56 chromosomes, confirming a tetraploid cytotype (2n = 4x = 56). Concurrently, flow cytometry (FCM) was utilized to conduct a precise genome estimation, yielding a nuclear DNA content of 2C = 1.93-1.99 pg for fresh material and 2.15-2.53 pg for herbarium. In addition, we identified one seedling with lower DNA content of 2C = 1.46 pg that most likely corresponds to F1 triploid hybrid between B. klokovii and B. pendula Roth. The results contribute significantly to our understanding of genomic evolution within the genus Betula L. and provide important insights into the taxonomy and conservation genetics of rare European birch taxa.