Karyological comparison between Iranian garlic (Allium sativum) ecotypes and foreign specimens

Abstract

Objective The first step in understanding a species’ genome is to study the number and shape of its chromosomes. Determining the relationship between species of a genus, traits such as chromosome morphology, absolute chromosome size, diversity in coloring, centromere position chromosome base number, and numbers of satellites must be considered. This study aimed to investigate cytogenetic diversity and to determine the relationship between native garlic ecotypes of Iran (Shahroud, Bojnurd, Mashhad, Birjand, Talish) with foreign specimens (originated from Turkmenistan, Azerbaijan, Tajikistan) and to prepare genome analysis based on chromosomal information. Materials and methods From the mitotic cells in the metaphase stage, which were prepared from the terminal meristem of the root and stained with acetoorcein, five suitable metaphase cells were selected and the length of short and long arms and the total length of chromosomes were measured using Karyotype Analysis Software (ver.1.5). Data were analyzed by JMP8 statistical software in an unbalanced completely randomized design. Mean comparisons were performed by Duncan test. To classify ecotypes, based on all chromosomal parameters, cluster analysis was performed using the Ward method. Results The results showed that the basic number of chromosomes in Turkmenistan and Bojnurd ecotypes was x=7, 2n=2x=14, and in other ecotypes x=8, 2n=2x=16. Short arm length, long arm length, and total chromosome length were significantly different (P≤0.01) between ecotypes. Cluster analysis divided the ecotypes into two groups. Minimum Euclidean distance observed between Azerbaijan and Talish ecotypes, the smallest chromosome belonged to Mashhad and the largest chromosome belonged to Shahroud. The most symmetric karyotype was Azerbaijan and the most asymmetric karyotype was the Shahroud ecotype. Conclusions The results showed that the differences in the number of chromosomes could be explained by Robertsonian translocations. It seems that the ecotypes with 2n=2x=14 chromosomes had more antiquity, and the ecotypes with 16 chromosomes originated from them. Considering that the Bojnourd ecotype with 14 chromosomes this region could be possibly introduced as the oldest origin or nuclear center of variation for garlic in Iran. Chromosomes also differ in the size and location of the centromere, which is due to chromosomal breakdown and the formation of a new structure in their reconnections. This study revealed which ecotypes are distant among the studied ecotypes, and also showed to produce possible future hybrids, in which direction will be more successful.

Keywords

• chromosomal diversity
• cluster analysis
• garlic
• karyotype analysis