Chromosome and ploidy analysis of winter hardy Hibiscus species by FISH and flow cytometry

Determination of nuclear DNA content, genome size, and ploidy level and, information on cytogenetic characteristics are all prerequisite of modern plant breeding. However, identification of individual chromosomes of Hibiscus species is extremely difficult due to high number, small size and similar shape of mitotic chromosomes. The goal of the study was to ascertain the chromosome number, karyomorphology, distribution of 5S and 18S rDNA signals, chromosome length, and centromere positions as well as the ploidy level, genome sizes, 2C - DNA content of winter-hardy Hibiscus (H. syriacus ‘Saejamyung’, H. sinosyriacus ‘Seobong’, H. moscheutos ‘Luna Red’ and, H. paramutabilis). 5S rDNA and 18S rDNA signals were detected by fluorescence in situ hybridization (FISH). According to the FISH results, there are two 5S rDNA signals (green) in H. syriacus, H. sinosyriacus, and H. moscheutos, and four 5S rDNA signals in H. paramutabilis. The range in length of somatic chromosomes in H. syriacus, H. sinosyriacus, H. moscheutos, and H. paramutabilis is 2.66–7.06, 3.18–7.31, 2.91–5.23, and 4.75–7.60, respectively. The 2C - DNA content of H. syriacus, H. sinosyriacus, and H. paramutabilis are very similar, the amount was 4.06, 4.11, and 4.18 pg, respectively whereas, H. moscheutos has nearly half and that amount was 2.06 pg. These findings will contribute to the detailed cytogenetic assessment of Hibiscus and thus benefit plant breeding in this genus.