New occurrence of b chromosomes in rheum tanguticum maxim. ex balf. (polygonaceae)

Abstract

A cytogenetic study was conducted on Rheum tanguticum populations from Huangnan Tibetan Autonomous Prefecture, China. The results revealed the chromosome numbers 2n=22 and the karyotype formulae are 2n=22=22m or 2n=22=2sm+20m, belonging to Stebbins 1A type. However, it was interesting to observe metaphases with variable B chromosomes (1, 2, 3, 4, 6, 7) in a few specimens. For the first time, the occurrence of B chromosomes was reported in natural populations of R. tanguticum. The number of B chromosomes in R. tanguticum varied not only among individuals but also within the same root tip. © 2011 Taylor and Francis Group, LLC.