First genome size assessment, heterochromatin and rDNA chromosome mapping in the genus Sclerocarya (Anacardiaceae): insight into the new basic chromosome number

Abstract

Sclerocarya birrea (Anacardiaceae) is a multipurpose plant characteristic of the Sahel Sudanian savanna that is found widespread across West Africa. As for most tropical trees and, generally, woody species, cytogenetic studies are scarce. Classical and molecular cytogenetic approaches have been used for the first time to study S. birrea subsp. birrea from Burkina Faso. Sclerocarya birrea is a diploid species that has a chromosome number of 2n = 28. Genome size, estimated by flow cytometry, was 2C = 0.81 pg. Two 35S loci and one 5S locus of rRNA genes were observed after fluorescence in situ hybridization. Six G-C-rich DNA regions, four corresponding to 35S signals and two corresponding to 5S signals, were detected by chromomycin A3 fluorochrome banding, but no DAPI-positive band was observed in this taxon.