Chromosome counts and karyotype analysis of species of family Apocynaceae from Egypt

Abstract

The chromosome counts of 13 species of family Apocynaceae in the flora of Egypt have been reported; one species from subfamily Periplocoideae and the other 12 species from subfamily Asclepiadoideae. The chromosome numbers are 2n = 22 for Periploca angustifolia, Glossonema boveanum, Pentatropis nivalis, Cynanchum acutum, Calotropis procera, Gomphocarpus sinaicus, Pergularia daemia and Pergularia tomentosa; 2n = 24 for Leptadenia arborea and Solenostemma arghel; 2n = 22, 44 for Caudanthera edulis, Caudanthera sinaica and Desmidorchis acutangulus. The chromosome numbers and karyotype analyses were firstly reported in Leptadenia arborea (2n = 24). The polyploid nature was demonstrated by the prevalence of cells with 2n = 4x = 44 chromosomes in Caudanthera edulis, Caudanthera sinaica and Desmidorchis acutangulus. The chromosomes are median and submedian as most species in the Apocynaceae. The intrachromosomal asymmetry and interchromosomal asymmetry were estimated with M_CA and CV_CL values. In intrachromosomal asymmetry, Desmidorchis acutangulus is the most symmetrical karyotype, while Pergularia tomentosa is the most asymmetrical karyotype. In interchromosomal asymmetry, Glossonema boveanum is the most symmetrical karyotype, while Cynanchum acutum is the most asymmetrical karyotype.