Efficiency Improvement of In Vitro Chromosome Doubling in Melon haploid

Abstract In vitro chromosome doubling (ivCD) using colchicine is a main method for melon haploid chromosome doubling, but its doubling efficiency remains low. In this study, we aimed to increase the efficiency of melon haploid doubling. In Experiment 1, the impacts of genotype and explant age on the survival rate (SR) and sample doubling rate (SDR) of melon haploid through ivCD were studied. Nine melon haploid genotypes were treated with colchicine for 24 hours followed by inoculation into solid MS. The best doubling effect was achieved with explant age of 21 days. During this process, the explants exhibited a low SR (38.76 ± 9.72%) and SDR (19.04 ± 7.10%), but a high vitrification rate (VR) (37.36 ± 9.93%) and an extended period for explant regeneration for over 30 days. In Experiment 2, four representative genotypes were selected to screen suitable combinations of antimicrotubular agents and hormone-treatments to enhance the SR and SDR, and solve the other problems above. The results indicated that treatment with trifluralin for 24 hours, followed by inoculation into solid MS medium containing 6-BA for 15 days, yielded the highest SR (72.27 ± 9.44%) and SDR (42.12 ± 9.72%), but the lowest VR (2.35 ± 4.25%) and a shortened regeneration period of 15 days. Interestingly, in Experiment 2, doubled haploid (DH) obtained from treatment with trifluralin performed better in pollen viability rate (PVR), pollen deformity rate (PDR), and seed germination rate (SGR) compared to those treated with colchicine. In summary, we significantly increased the haploid chromosome doubling rate, reduced the regeneration time, and obtained DHs with relatively high fertility.