# Verification of the chromosome number using cytogenetics and estimation of genome size via flow cytometry and k-mer analyses for representative Anoectochilus roxburghii accessions

## TL;DR

This study determines the chromosome number and genome size of Anoectochilus roxburghii using cytogenetics, flow cytometry, and sequencing, providing a foundation for future genetic research.

## Contribution

The study provides the first chromosome count and genome size estimation for A. roxburghii using multiple methods.

## Key findings

- A. roxburghii has a chromosome number of 2n = 80 with no sex-linked heterotropy.
- Genome size of Luofushan-1 was estimated at approximately 5.68 Gbp via k-mer analysis.
- DNA content among accessions ranged from 6.57 to 8.26 pg using flow cytometry.

## Abstract

Anoectochilus roxburghii (Wall.) Lindl. is a perennial herb of orchidaceae. Because of its functions of heat-clearing and blood-cooling, removing dampness, detoxification and enhancing immunity, it is considered as a nutritious medicinal plant with high economic value. Originating from Guangdong province, China, chromosome number and genome size of A. roxburghii (“Luofushan-1”) were determined through cytogenetics, flow cytometry, and k-mer analysis. We analyzed the karyotype of A. roxburghii using different cytogenetic markers, and the results showed a chromosome number of 2n = 80, but no sex-linked chromosome heterotropy was observed. For flow cytometry analysis, tomato and maize were used as internal standard, and the 2C DNA amount among sixteen Anoectochilus accessions ranged from 6.57 to 8.26 pg (including Luofushan-1). Additionally, a genome survey of “Luofushan-1” was performed using Illumina HiSeq 2000 DNA sequencing, k-mer analysis revealed that the genome size of “Luofushan-1” was approximately 5.68 Gbp. This comprehensive study establishes a foundation for subsequent whole-genome sequencing of A. roxburghii, contributing valuable insights into its genetic characteristics and paving the way for further research on this medicinal plant.