| The inhibitor of ethylene AgNOs was first used on in vitro gynogenesis in melon. Haploid was obtained. Cytological analysis on the gynogenesis showed that egg apparatus in embryo sac developed into embryoid.In late May, ovaries of melon (Cucumis melo L. cv. 2B39) excised 14h before anthesis were peeled by hands to make the ovules just out of the ovary. Longitudinally sliced ovaries were surface sterilized, inoculated on pretreatment medium A under 35℃ for 4 days in the dark, then transferred to induction medium B supplemented with different AgNO3 concentration 0, 5, 10, 15, 20, 30, 40, 60, 80, 160 mg.L-1 for two weeks under 25℃ with a 16/8h (light/dark) photoperiod. Following the induction period, the ovules were removed from the placenta, transferred to elongation and regeneration medium C. Six ovules developed into plantlets by direct embryoids., Results from the regeneration test indicated that 80 mg.L-1 AgNO3 was favoured to the efficiency of gynogenesis, the percentage of embryos reaching 0.74%. By micropropagation and subculture, six regenerants were subdivided into 12 plantlets. Through the number of chloroplasts in guard cell for the ploidy level among the plantlets survived, one is haploid, one is triploid, one is tetraploid,others are mixoploid. Cytological observation on gynogenesis showed that at 14h before anthesis, the embryo sacs have formed the eight nuclei structure, the two polar nuclei still separate each other. After 4 days heat treatment, some of the gametophytes have proliferated into multi-celled proembryos. After inoculation for 18 days, the shape of the embryoid can be seen clearly in the embryo sacs, showing the embryoid was initiated directly from egg apparatus. In August, inoculation by peeling the ovaries and cutting the ovary into slice, under the identical culture condition no regenerant was obtained, which indicated that both the physiological condition of the donor plants and the approaches of inoculation affect the gynogenesis.
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