Efficient Parthenogenesis Induction and In Vitro Haploid Plant Regeneration in Cucumber (Cucumis sativus L.) Using Putrescine, Spermidine, and Cycocel

Abstract

In this study, the effect of spraying mother plants with various levels of putrescine, spermidine, and cycocel (each at 0, 50, 500, and 5000 mg/l) were assessed on the frequency of haploid embryos produced from unfertilized ovaries and subsequent regeneration of derived embryos. Significantly higher haploid embryos were obtained when mother plants were sprayed with putrescine at 500 mg/l (5.2 embryos/fruit), spermidine at 50 mg/l (4.8 embryos/fruit), and cycocel at 50 mg/l (5.2 embryos/fruit) as compared to the control (without spraying, 3.2 embryos/fruit). However, embryogenesis induction was decreased drastically as the concentration of all the three compounds tested was increased and the lowest haploid embryos were observed when 5000 mg/l of spermidine (0.4 embryos/fruit) or cycocel (2.0 embryos/fruit) were applied. Only spermidine at 50 mg/l led to 100% regeneration into fully developed plantlets. The seed setting and size of fruits were also affected by polyamines and cycocel applications. Ploidy analysis using a flow cytometer indicated that all regenerated plantlets contain the gametic chromosome number (n = x = 7) of parental plants and the results of chromosome counting also confirmed the haploid nature of regenerated plantlets. It can be concluded that the induction of haploid embryogenesis from unfertilized ovaries after pollination with irradiated pollen and subsequent conversion of derived embryos into the plantlets could be improved in Cucumis sativus L. by applying appropriate levels of putrescine, spermidine, and cycocel.