Study On In Vitro Culture Unfertilized Ovule In Watermelon(Citrullus Lanatus)

Haploid cultivation has ability to obtain homozygous genotypes rapidly, which can be used as new germplasms; Compared with conventional breeding protocols, haploid cultivation can accelerate the breeding progress and expand breeding approaches. The haploid material can be used for gene mapping and genetic maps building. Usually, haploid materials can be obtained through gynogenesis or androgenesis induction. Previous studies on haploid induction in watermelon has carried out both in china and aborad.Compared with pollination by radiation pollen, anther culture and the in vitro culture of unfertilized ovary, unfertilized ovule in vitro cultivation has hardly been reported. Otherwise, Some other cucurbitaceae crops, such as pumpkin(Cucurbita moschata Duchesne), cucumber(Cucumis sativus Linn.), melon(Cucumis melo L.), pumpkin(Cucurbita pepo L.),have obtain haploid by inducing gynogenesis in vitro. Based on previous studies, watermelon unfertilized ovules cultivation in vitro was used to explore the possibility of obtaining haploid plants through in vitro cultivation. and determine the influencing factors during the cultivation. Our goal is to provide the theoretical basis for the establishment of highly efficient and stablely system in vitro culture of unfertilized ovules in watermelon. The main results are as follows:1. Researches on the affecting factors of callus induction.(1) Genotype: Genotype was main factor for callus induction.the 8 materials showed significant difference in reaction rate and the callus induction rate. The highest callus induction rate was ’zhongke 6’( 92.3%) and the lowest was wild materials ‘09005’(57.2%).(2) Low temperature pretreatment: The low temperature pretreatment were not significantly improve the ovule reaction rate and the callus induction rate, the ovule reaction rate and callus induction rate were influenced by culture medium.(3) High temperature pretreatment: The yield of ovule reaction rate and callus increased apparently by 35 °C higher temperature preculture, 3d pretreatment can get higher callus induction rate and improve the callus quality.(4) The medium: This experiment use the orthogonal design selection of 25 kinds of induction media, include 6- BA and NAA which had important effect on start the ovule reaction and callus growth. the callus induced by 2, 4-D were hard to differentiation. It was bad for ovule reaction and callus generating adding ABA in medium.2. Researches on the affecting factors of the regeneration plant.(1) Genotype: This experiment use the ’daguoheimeiren’, ’xinong 8’ and wild watermelon ’09005’ as the material to induce regeneration plant. The wild watermelon ’09005’ didn’t get the regeneration plant, while other two materials obtained regeneration plants.(2) Sampling time: We compared samples in the flowering date and 1 day after the flowering date found that sampling in 1 day after flowering date was better than that of flowering date.(3) The medium: Low levels of the hormone concentration combination 6-BA 1 mg/L + 0.5 mg/L NAA + TDZ 0.05 mg/L was more suitable for induction of regeneration plant. Adding casein hydrolysate in medium is beneficial to the growth of ovule and 600 mg/L was recommended.3. A lot of callus through the induction of unfertilized ovules in watermelon,make paraffin section for unfertilized ovules to observation the source of callus, the results show that: the integument easier to produce callus, and those callus was hard to differentiate.4. In vitro culture unfertilized ovule in watermelon,we obtain 3 regenerated plant, test the SSR molecular identification of the regeneration plant, prove that the regenerated plant is homozygous genotypes.This is possible to obtain regenerated plant through in vitro culture of unfertilized ovule.Provide the reference for establish highly efficient and stablely system in vitro culture of unfertilized ovules in watermelon.