Karyotype analysis and genome size estimation of Sapindus mukorossi Gaertn. an economical important tree species in China

Sapindus mukorossi Gaertn. is a multi-purpose tree used for landscaping and ecological protection, and in the chemical and wood oil industries in China. However, the karyotype and genome size of S. mukorossi are currently unknown, which has hindered the development of novel cultivars and identification of Sapindus species. In this study, we characterized the karyotype and estimated nuclear DNA content of S. mukorossi from southern China. The S. mukorossi karyotype was characterized by 2n = 2x = 28 = 12sm + 16 m, and the karyology analyses of trees from Fujian, Jiangsu, and Zhejiang Provinces gave an average relative chromosome length of 19.13, 22.01 and 22.45 & mu;m, karyotype asymmetry index of 59.78, 60.60 and 60.03, mean centromere index of 38.27, 39.26 and 39.68, and chromosome types classified as "2B", "2B", and "1A", respectively. Using the known genome size of poplar as a standard species, with internal and external standard methods, the genome size in Fujian, Jiangsu, and Zhejiang Provinces was 414.215 & PLUSMN; 0.96, 444.55 & PLUSMN; 10.12 and 439.67 & PLUSMN; 2.01 Mbp; the average size of about 432 Mbp represents a small genome. This study is the first report about karyotype for S. mukorossi and will facilitate future cytogenetic and omic studies of this species, and could serve as a reference for studies on other species related to this genus.