Chromosome counts and karyotype analysis of Viburnum taxa (Adoxaceae)

摘要

A cytological study was carried out on 16 taxa belonging to seven clades of Viburnum (Adoxaceae). Chromosome numbers of these 16 taxa were counted and karyotypes of 12 taxa were analyzed. Chromosome numbers of four species and karyotypes of nine taxa are new records. Three chromosome numbers 2n = 16, 18 and 32 of these 16 taxa were discovered, of which the corresponding basic chromosome number was x = 8 or 9. Most taxa showed relatively symmetrical karyotypes, while the well-known V. macrocephalum form. keteleeri, which has a long cultivation history and is culturally important in China, presented the most asymmetrical karyotype. Unweighted pair group method with arithmetic mean (UPGMA) cluster analysis of V. cylindricum and V. punctatum supports the recognized clades Coriacea and Punctata that were previously subsections of Megalotinus. The chromosomal pattern with few polyploids suggests that structural changes of karyotype at the diploid level may be the main trend in chromosomal evolution in Viburnum.