# Optimization of Chromosome Preparation and Karyotype Analysis of Winter Turnip Rape (Brassica rape L.)

## TL;DR

This study optimizes techniques for preparing and analyzing chromosomes in winter turnip rape, revealing insights into its karyotype and evolutionary origins.

## Contribution

The study establishes optimal conditions for chromosome preparation and provides a detailed karyotype analysis of winter turnip rape.

## Key findings

- Optimal conditions for chromosome preparation include sampling at 8:00–10:00, 20 h ice-water pretreatment, and specific fixation and dissociation methods.
- Winter turnip rape has 2n = 20 chromosomes with a karyotype formula of 2n = 2x = 20 = 16m + 4sm.
- The karyotype asymmetry coefficient is 58.85%, suggesting it may represent an evolutionarily primitive type (type 2A).

## Abstract

To explore the dyeing technique and karyotype analysis of winter turnip rape (Brassica rape L.), the root tip of winter turnip rape Longyou 7 was used as the experimental material. Chromosome preparation technology was optimized, and karyotype analysis was carried out by changing the conditions of material collection time, pretreatment, fixation, and dissociation. The results showed that the optimal conditions for the preparation of dyeing winter turnip rape were as follows: the sampling time was 8:00–10:00, the ice–water mixture was pretreated at 4 °C for 20 h, the Carnot’s fixative solution I and 4 °C were fixed for 12 h, and the 1 mol/L HCl solution was bathed in a water bath at 60 °C for 10~15 min. Karyotype analysis showed that the number of chromosomes in winter turnip rape cells was 2n = 20, and the karyotype analysis formula was 2n = 2x = 20 = 16m + 4sm. The karyotype asymmetry coefficient was 58.85%, and the karyotype type belonged to type 2A, which may belong to the primitive type in terms of evolution. The results of this study provide a theoretical basis for further in-depth study of the phylogenetic evolution and genetic trend of Brassica rapa.