Studies Of In Vitro Culture Of Unpollinated Ovules In Melon (cucumis Melo L.)

Melon(Cucurbita melo L.) is one of the most important gourd vegertable crops in the world.It has obvious hybrid vigor.And it is very difficult to obtain self-bred lines.It needs many years and lots of work to select excellent self-bred lines.So,Decreasing selection cycle time can improve breeding pace obviously.It is necessary to find a new way for getting excellent self-bred quickly.Haploid breeding technique can provid a quick way to obtain good self-bred lines.The breakthrough of in vitro culture of unpollinated ovaries and ovules indicates that it may become an alternative way to haploid breeding.It means that not only the microspore but also the megaspore or femele gametophyte of angiosperms can be triggered in vitro to sporophytic development,thus opening a new way to genetical research and haploid breeding.We can use this method in melon to improve the rate of breeding.Many kinds of embryoid sac plants can be obtained through in vitro culture of unpollinated ovules in plants.Those embryoid sac plants can enrich melon germplasm resources such as haploid,double haploid(DH), polyploid and aneuploid.The high purity of doubled haploid plants can be obtained from doubling haploid plants.Therefore,the haploid and doubled haploid plants are very useful for breeding as source materials.And the DH plants can be used as the ideal lines to RFLP and the establation of the genetic map.Thus,the experiment is very important for theory research and breeding application.This research studied three donator materials T03-1,"Yilishabai" and T13-1.They are from different ecological type.Several factors were set to study the effect of in vitro culture of unpollinated ovules in melon.These factors contain basal medium,hormones, AgNO₃ and so on.The research results as follows:(1) Ovaries donor of melon were collected 14 hours prior to anthesis.The ovules were peeled out of the ovary in the lab.Then the sliced ovules were surface sterilized, followed by incubation on pertreatment medium under 35℃for 4 days in the dark to induce gynogenesis.(2) To find the most suitable way of sterilization for in vitro culture of unpollinated ovules in melon,the research set different sterilization concentration and different sterilization time.The examination also compared the three melon varieties and planting seasons.The result clearly showed that the explant in autumn need less sterilization concentration and sterilization time than in spring.In addition,all of the three melon species have the same conclusion.The genotype is the important factor for in vitro culture of unpollinated ovules.(3) Most of ovules of T03-1 turned brown and died gradually after inoculation. T13-1 has the highest buds formation frequency(3.3%) by adding 0.5mg/L 6-BA and 0.05mg/L NAA.And the highest callus formation frequency(3.3%) was recouded by adding 0.2mg/L 6-BA and 0.05mg/L NAA in melon species "Yilishabai".(4) The highest buds induction rate is 36.7%by adding 20mg/L AgNO₃ in T13-1.