3.3 | Karyotype analysis and chromosome pairing at metaphase I
Karyotype analysis showed that R. stricta , R. turczaninovii and putative hybrids were tetraploids (2n = 4x = 28) (Figure 4). The meiotic configurations of the possible parent and the putative hybrids were listed in Table S2.
Meiosis of R. stricta and R. turczaninovii were quite regular with 14 bivalents (Figures 5a-c, Table S2). Meiotic pairing in 17 hybrids RH1 were comparatively high, with an average of 0.98 univalents and 13.52 bivalents per cell with c-value of 0.89 (Figures 5d, e; Table S2). Chromosome pairing in 40 hybrids RH2 were comparatively high with an average of 0.85 univalents and 13.55 bivalents per cell with c-value of 0.90 (Figures 5g, h; Table S2). Except for hybrid RH2-31, all hybrids had univalent. In all hybrids, the c-value was higher than 0.81, suggesting that chromosome pairing of the hybrids was comparatively regular and two sets of genomes in hybrids were homology.
At the same time, some lagging chromosomes and chromosome bridges were observed at anaphase I. (Figures 5f, i).