Comparative Study On Diploid And Autotetraploid Chinese Jujube

Chinese jujube (Ziziphus jujuba Mill.) originated in China and it belongs to Ziziphus genus, Rhamnaceae family. It is widely cultured, and has the greatest economic value in the known Ziziphus genus. 'Zanhuangdazao' is the unique known natural triploid and the rest were diploid. There are some advantages of 'Zanhuangdazao', for example, large fruit, strong adaptability, high yield etc. In view of the advantages of polyploidy, in recent years, colchicine was used to induce mutation of shoot tips by Research Center of Chinese Jujube. Tetraploid'Dongzao','Lajiaozao'and'Linyilizao'(being identified by using flow cytometry instrument) have been successfully induced. The cytological, morphological and DNA variations of Chinese jujube were studied to provide reference of using these new germplasms in cultivation and breeding, as well as add new content to studies of genetic variation autopolyploid. The main results are as follows:1. Diploid and tetraploid'Dongzao','Lajiaozao'and'Linyilizao'were used to study the mitosis. The cells which have 48 chromosomes accounted for 86.67%, 89.19% and 87.10% respectively of the total number of cells observed in metaphase.2. AFLP was used to identify differences of DNA between diploid and tetraploid. The result showed that, the differences were not significant.3. Autotetraploid Chinese jujube were characteristic of wider and thicker leaves, smaller leaf index, smaller stomatal density and larger guard cells. In autotetraploid, the number of chloroplasts in guard cells increased, pollen viability decreased, the size of pollen increased significantly and four holes ditch pollens were observed.4. Meiosis of pollen mother cells (PMCs) in diploid and autotetraploid'Dongzao','Lajiaozao'and'Linyilizao'were observed, and all stages of the meiosis were analyzed. Compared with meiosis in diploid, the behavior of meiosis in autotetraploid was much more complicated than that in diploid. Diakinesis, univalents, bivalents, trivalents and quadrivalents appeared in autotetraploid'Lajiaozao', while two nuclei, including a large one and a small one, were observed. Some of the chromosomes were found not being arranged on equatorial plate at metaphaseâ… and metaphaseâ…¡followed by lagged chromosomes and chromosome bridges appeared at anaphaseâ… and anaphaseâ…¡in the autotetraploid. At tetrad stage, dyads, triads with micronucleus, tetrads with micronucleus appeared. In conclusion, abnormal meiosis of PMCs is the cytogenetic reason for fertility reduction in autotetraploid'Lajiaozao'.