Syntesis Of Doubled Haploid And Homologous Tetraploid Melon (Cucumis Melon L.) And Relevant Studies On The Two Materials

Doubled haploid '4810' was produced by treating melon(Cucumis melo L.) buds in vitro with colchicine.Homologous tetraploid melon was obtained via clonal variation from immature embryo cotyledon culture.Studies were carried out on physiology and biochemistry indexes of doubled haploid and quality,meiotic chromosome behavior and fertility of tetraploid,as well as propagation of the two materials in vitro.1.Induction of Doubled Haploid and Its Preliminary Qualitative Studies on Melon (Cucumis melo L.)Two experiments,immersion of haploid buds in colchicine and culture of haploid buds in the medium with colchicines,were carried out to induce doubled haploid melon.The best result was obtained by immersing the buds in 0.025%colchicine for 8 hours.The doubling ratio was 13.7%.We observed the morphology and measured some physiological and biochemical parameters with comparison of the haploid,doubled haploid and regular diploid melon plants.The results indicated that the leaf,stem and flower of doubled haploid are bigger than haploid and close to the diploid,and total chlorophyll,chlorophyll a, chlorophyll b and soluble protein contents in double haploid were higher than haploid respectively,and the difference of soluble sugar contents was not distinct.The EST isozyme electrophoresis revealed that haploid and doubled haploids lost two bands comparing the diploid plants.2.Induction of Homologous Tetraploid and Its Preliminary Qualitative Studies on Melon(Cucumis melo L.)We iuduced homologous tetraploid melon through clonal variation from immature cotyledon culture.In the culture,there were six genetypes melon,and the ratio of differentiation,variation and doubling were different on the different genetype and incretion concentration.We obtained homologous tetraploid melon 'QiTian YiHao',which the most effective concentration of BA was 3.0 mg/L,and the doubling ratio was 14.3%.We observed the morphology of diploid and homologous tetraploid melon,and mensurated several index of quality.The results shows that the morphologic indexes of stem,leaf,flower,fruit and seed of tetraploid were all bigger than diploid except the fruit shape index.At the same time,Vc and soluble sugar content of homologous tetraploind were all higher than diploid melon.Cytological studies were conducted on pollen mother cells(PMCs) meiosis of homologous tetraploid melon using chromosome preparation technique.Results showed that the PMCs meiosis of the homologous tetraploid melon was similar to the diploid.However,there were particularities.In pachytene,there were 6.7%cells with double nucleolus.In diakinesis,bivalen,multivalent,trivalent and univalent were observed.Some of the chromosomes were found not to rank at the equator in metaphaseâ… and metaphaseâ…¡cells.In anaphaseâ… and anaphaseâ…¡,there were chromosomes bridges and lagging chromosomes.At tetrad stage,dyad,triad,tetrad and polyad appeared.Abnormal meiosis of PMCs was the cytogenetic reason for fertility reduction of homologous tetraploid melon.3.Studies on Propagation of Doubled Haploid and Homologous Tetraploid Melon in vitroIn order to setup the propagation system of doubled haploid and homologous tetraploid melon in vitro,we investigated the condition for propagation using shoot-tips as explants.Results indicated that the optimal culture medium for propagation and elongating growth of doubled haploid and homologous melon were MS+BA0.5mg/L and MS+BA0.3mg/L respectively.The optimal culture medium for rooting of doubled haploid was 1/2MS+IBA0.5mg/L,and for homologous tetraploid melon was 1/2MS+IBA0.8mg/L.