珍稀药用植物桃儿七的核型分析及基因组大小鉴定OA

Sinopodophyllum hexandrum(Royle)Ying,a rare,endangered and national second-class protected medicinal plant of the Berberidaceae family,is of considerable value for pharmaceutical development and phylogenetic research.However,the species has long been plagued by controversies regarding its chromosome base number(x=6 vs x=7),and no reports on its genome size are available.In this study,seedlings germinated from wild S.hexandrum seeds collected from Zhuoni County,Gansu Province,were used as materials to systematically analyze key cytogenetic characteristics via the conventional squashing method and flow cytometry(FCM).The results from the squashing method showed that the somatic chromosome number of S.hexandrum was stably 2n=12,with a chromosome base number of x=6.The karyotype formula was 2n=12=8m+4sm,consisting of 8 metacentric chromosomes(m)and 4 submetacentric chromosomes(sm).The relative length of chromosomes ranged from 11.11%to 20.57%,the arm ratio varied from 1.29 to 1.95,the ratio of the longest to the shortest chromosome was 1.85,and the asymmetry coefficient(As.K%)was 59.67%,indicating a typical 2A-type karyotype.For flow cytometry analysis,Zea mays(2C=4.71 pg)and Hordeum vulgare(2C=9.79 pg)served as internal reference standards.The results exhibited distinct separation of fluorescence peaks with no interfering signals,and the coefficient of variation(CV)was<5%,thus confirming the reliability of the assay.The C DNA content of S.hexandrum was determined to be 17.14-17.88 pg,corresponding to an estimated genome size of 16.76-17.49 Gb,which classifies this species as a typical large-genome plant.This study thus represents the first comprehensive investigation to clarify the integrated cytogenetic characteristics of S.hexandrum and resolve the long-standing controversy regarding its chromosome base number.Furthermore,the species'highly symmetric karyotype provides robust support for its primitive evolutionary position within the Berberidaceae.The results can provide critical cytological evidence for elucidating the speciation mechanism and interspecific phylogenetic relationships of S.hexandrum,while laying a robust foundation for experimental design,data calibration in subsequent whole-genome sequencing,and phylogenetic reconstruction of the Berberidaceae.