Genome size identification and karyotype analysis of Sagittaria trifolia

Abstract [Objective] Sagittaria trifolia is an important horticultural and cash crop in China. Identification of genome size and analysis of karyotype are essential for genome research and molecular genetics of S. trifolia. Currently, the genome size and chromosome morphology of S. trifolia are unclear. The present study provides cytological references to S. trifolia breeding and species evolution analysis. [Methods] Using flow cytometry and fluorescence in situ hybridization, together with reference to the lysate formulation to probe configuration, the genome size of the root tips of S. trifolia variety ‘Zijinxing’ (ZJX) was identified and the chromosome morphology was analyzed. [Results] (1) The tested cecropia was a diploid plant, and the genome of ‘Zijinxing’ cecropia was about 16 Gb. (2) Using DAPI fluorescence staining, the number of chromosomes was identified to be stable, consistent with the results of telomeric fluorescence in situ hybridization. The chromosome types were middle mitotic (metacentric chromosome), near-middle mitotic (submetacentric chromosome), and proximal mitotic (acrocentric chromosome), with the most centromere was found in the proximal part, and no satellite was found. The karyotype formula was 2n=2x=22=6m+4sm+12st, belonging to the type 3B of Stebbins, with the asymmetry coefficient of 99.13. [Conclusion] The study concludes that the genome of S. trifolia is of medium size, with a highly asymmetric karyotype and a high degree of evolution.