Studies On Callus Induction And Plantlet Regeneration Of Triploid Citrullus Lanatus

This work was mainly studied germinating of triploid Citrullus lanatus on germ-free condition, callus induction, subculture, differentiation and plantlet regeneration. The high efficiency system for callus amplification of triploid Citrullus lanatus was established. All the results were beneficial to somatic embryogenic cell induction, character of somaclonal variation and cell engineering of triploid Citrullus lanatus. The results indicated:The seeds of triploid Citrullus lanatus were surface sterilized as follows: (1) Rinsing with 75% alcohol for 30s. (2) Sterilizing with 10% bleaching powder and 0.5% NaClO for 30min and washing with sterile distilled water for 5min (3 to 5 times). The best germination occurred on the condition of the seeds in vermiculite media or agar media. The seeds were cultured in dark for three days and then transferred into culture room. After seven days, the sound seedlings were sprouted. The germination of seeds on germ-free condition had no relation to variety genotype. They would germinate normally if only the seeds in suitable conditions of light, temperature, water and air.The best explants were hypocotyl and cotyledon of the seedlings which were two to six days old. The most suitable medium for callus induction to triploid Citrullus lanatus was MS+NAA 1.0mg/L+BA 0.5mg/L. It would take one week in darkness that the callusogenesis of the explants was switched on, then the callus amplification and its further differentiation must be in light. Significant differences of callus inductive rate and index of induction were found among the various genotypes ofexplants cultured in C24 medium. In C24(MS+NAA l.Omg/L+BA 0.5mg/L) medium, "Heimi 5 Hao" was the easiest one to induce callus. It would be a perfect material for somatic embryogenic cell induction of triploid Citrullus lanatus.Enormous differences of callus inductive rate and index of induction were found among the different sugar source. Sucrose was the best one, glucose came second. Lactose, maltose and sorbose were disadvantageous to the induction and growth of callus. Considerable differences of callus inductive rate and index of induction were found among the different sucrose concentration too. When its concentration was above 3%, the rate of induction was descent. But when the concentration was increased properly, it was advantageous to its further differentiation. As far as the rate and the texture of callus were concerned, the most suitable sucrose concentration was 5%.In order to increase the speed of callus propagation, sucrose concentration would be lowered properly. As for "Heimi 5 Hao", the proper concentration was 2%. The most suitable media for inducing adventitious buds from callus was MS+BA4.0mg/L+NAA0.5mg/L. The percentage of adventitious buds was 75% on the media and the adventitious buds developed normally. The mutiplication coefficient of adventitious buds was exceed eight when the adventitious buds were cultured in the media of MS+BA2.0mg/L+IBA0.5mg/L(or MS+BA4.0mg/L+IBA1.0mg/L). The efficient buds percentage was 93.52% and there were not any callus. The adventitious buds stretched fast in the medium of MS+KT (0.2mg/L or 0.5mg/Lor 1.0mg/L).The stretched shoots rooted easily in the medium of 1/2MS +IAA0.4mg/L (or IBA0.3mg/L). The rate of root induction was 100% and there were not any callus.Most of the rooted plantlets of triploid seedless watermelon survived with a survival rate of 97.5% with the method as follows: six to eight days supplemental lighting treatment outside laboratory firstly, then transfer them in sterile distilledvermiculite + trurfy soil (1/2 V:V) mixture. And the microplants were strong.