| Balsam pear (Momordica charantia L.) is a familiar melon vegetable. In these years, it has been proved that balsam pear has many components which have various medical functions, such as decreasing blood sugar, resisting tumors and enhancing immunity and so on. Therefore, as a healthy food, balsam pear was in great need, and now it is extensively cultivated in China. In this paper, effects of plant growth substances, genotypes and explants on callus induction, adventitious bud and root induction were compared using the superior balsam pear cultivars, and an efficient in vitro plant regeneration system in balsam pear was established. The histology of direct shoot organogenesis from explants of balsam pear was studied as well. In addition, the content of endogenous hormones in balsam pear during in vitro culture was measured. It will provide a theoretical evidence for studying the regulation mode of organogenesis in balsam pear. The main studies and results were reported as following: 1. Obtainment of sterile seedlings of balsam pearThe balsam pear seeds were selected as primal material and cultured on 1/2MS medium to obtain sterile seedlings. The results showed that pretreatment that seeds were dipped in 55C water for 10 minutes and continuous dipped for 16 hours was of benefit to increase the rate of germination by 20 percent. The following treatment was that, seeds were get rid of outside seed coat, then in 10%NaClO4 solution for 15 minutes, followed by cultured on 1/2MS medium in darkness for 5 days, finally cultured in light for 14 hours per day. By this way, rate of germination was increased and sterile seedlings grew well. Theresults also indicated that some obvious differences were observed in various balsam peargenotypes, even which were cultured in the same medium and in the same culturecondition.2. Establishment of in vitro plant regeneration system in balsam pearThe effects of plant growth substances and explants on the organogenesis of balsam pear were investigated by using the orthogonal test. The results showed that the optimal medium for callus induction and callus growth was similar, MS + 6.0 mg/L ZT + 1.0 mg/L KT, but effects of three factors on callus induction and callus growth were different. Among the three factors, ZT was the most important factor for callus induction, then KT and explants. The cotyledon was the best explant for callus induction. Meanwhile, explant was the most important factor for callus growth, followed by ZT and KT. The hypocotyl was the best explant for callus growth.The results showed that adventitious buds could be induced by adding ZT and KT to MS medium. The medium supplemented with 2.0 mg/L ZT and 0.5 mg/L KT was beneficial to induce more adventitious buds and increase the rate of adventitious buds induction to 13.21 percent. And it didn't increase the rate of adventitious buds to add TDZ or ABA to medium additionally. The epicotyl from Binjiang No.l, as experimental material, was advantageous for inducing more adventitious buds.In addition, the histology of direct shoot organogenesis from explants of balsam pear was studied. Histological observations indicated that the adventitious buds had apical meristem, leaf primordium, axillary bud primordium and young leaves, which were the typical bud structures.The rate of adventitious root induction was influenced by many factors, among which NAA was the key factor. The suitable medium for adventitious root induction was MS + 0.5 mg/L NAA. In addition, the rate of adventitious root induction was different depending on different explants, that of epicotyl and hypocotyl was above 70% respectively, while that of cotyledon was only 26.76%.Based on the above-mentioned results, a simple protocol for plant regeneration of balsam pear was developed: epicotyl explants were cultured on the medium of MS + 2.0 mg/L ZT + 0.5 mg/L KT, and then the adventitious buds were cut and transferred to the medium of MS + 0.5 mg/L NAA. Some adventitious roots were produced and perfect plantlets were formed.
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