Karyomorphological study and its correlation with the quantity and quality of essential oil in Iranian chamomile accessions (Matricaria chamomilla L.)

The genetic vulnerability of crops resulting from genetic diversity depletion is one of the breeders' main concerns. Therefore, wild species play an essential role in developing gene pools and improving some of the crops' agronomic characteristics. Iran country is considered a natural habitat of chamomile. In this study, six diploid accessions and two tetraploid varieties were evaluated for karyotype characteristics and phytochemical variation. Cytogenetic studies were carried out by squash method and using digital analysis. Karyotype parameters were analyzed in a completely randomized design (CRD) factorial with five cell replicates. Phytochemical properties were evaluated at the full flowering stage. Main compounds were identified by gas chromatography-flame ionization detection (GC-FID) and gas chromatography-mass spectrometry (GC-MS) analysis. Karyotype analysis of diploid (2n = 2x = 18) and tetraploid (2n = 4x = 36) chamomile (accessions, varieties) showed that the chromosomes were small, ranging from 1.87 ± 0.05 μm to 4.24 ± 0.12 μm. Based on the karyotypic formula, the genotypes had two types of chromosomes (m, sm) mostly. Karyotype parameters including symmetry and asymmetry indices were estimated. Ramhormoz and Zloty Lan genotypes were the most and the least asymmetric karyotype, respectively. According to the cluster analysis based on Ward's method, the dendrogram demonstrated three groups. The principal components analysis results showed that the first three components covered 77.7% of the data variation. The essential oil content in diploid accessions ranged from 0.36% (Taft) to 0.86% (Andimeshk), and tetraploid varieties had 0.39% and 0.48% essential oil (Budakalazi and Zloty Lan, respectively). The essential oil compounds had a high-level of variation in studied genotypes. •Iranian natural chamomile accessions have a high-level variation.•The Karaj accession is more substantial for breeding improved new varieties.•The Chamazulene has positively correlation with chromosome length (S + L).•Essential oil percentage has negatively correlation with chromosome length (S + L).