| Watermelon [Citrullus. lanatus (Thunb.) Mansf] is the annual herbaceous crop and is atypical monoecious crop belonging Cucubitaceae family. The watermelon has three types offlowers: male, female and hermaphrodite flower. According to the floral organ compositionand growth section, the watermelon sexual type includes monoecious, gynoecious,andromonoecious, hermaphrodite and so on. Research in sex differentiation of watermelonwill cultivate gynoecious varieties to be used in production, and can promote the watermelonseed industry revolution. It also will effectively reduce the cost of seed production, andimprove the efficiency and purity of seed.The flower buds from three kinds of sexual type (monoecious, gynoecious andandromonoecious) at different development stages were made into paraffin section forcytomorphological observation. The research showed that the cytological and morphologicaldifferences between three kinds of sexual type and speculated the demarcation point of sexdifferentiation development process. In order to obtain the more information about therelationship between sex determination candidate gene ClACS-7and sex determination ofwatermelon, the present experiment was carried out to study the expression of ClACS-7geneof both different flowers and different developmental stages of flower by real-time fluorescentquantitative PCR. The research had showed that the correlation between ClACS-7gene andsex differentiation of watermelon.The results obtained as following:(1) The floral primordial processes from three kinds of sexual type in watermelon beforehermaphrodite stage and the same sex floral organ development process had no significantdifferences.(2) When the length of flower bud was about0.8-1mm, the cytomorphologicaldifferences of male, female and hermaphrodite flower began to happen. Stamen primordiavolume of male and hermaphrodite flower augmented rapidly, and carpel primordia of femaleand hermaphrodite flower began to differentiate into stigma and ovary. Compared to male andfemale flower, the length of hermaphrodite flower bud was longer after hermaphroditic stage.(3) There were some deformed female flowers in gynoecious. The base of carpelprimordia would stop the development after denting to a certain degree, while the stamenprimordia would not stop elongation and develop to form the mature stamen with smallamount of mature pollen grains.(4) The ClACS-7gene expressed both in watermelon hermaphrodite and female flower, not in male flower. It deduced that ClACS-7gene was related to watermelon female primordiadifferentiation. The highest expression of ClACS-7gene happened in the hermaphrodite stageof hermaphrodite and female flower. Preliminary viewed that: the hermaphrodite stage wasthe demarcation point of watermelon sex differentiation process. |
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