Abstract: The methods of eliminating walls by enzymolysis and low osmosis were used to analyze
the chromosome karyotype of Ziziphus jujuba Mill.‘Pingguozao’. The results showed that the karyotype
formula was 2n = 3x = 36 = 21m + 15sm（2SAT），and the karyotype was 2A type. It was second of the
newly discovered natural triploid cultivar. The meiosis course of pollen mother cells of‘Pingguozao’was
observed，and the various periods of the meiosis were described and analyzed. The results showed that the
meiosis of ‘Pingguozao’was irregular. The diakinesis appeared univalent，bivalent and trivalent，and 57.5%
of them were trivalent，at least 7 trivalents，at most contained 10 trivalents. The three genomes had very
high homology. The lagging chromosomes and chromosome unequal separation phenomenon were
observed in anaphase I and II. Some cells also produced few triad and pentad in telophaseⅡ，and formed
unequal spores，and led to highly gametophyte sterility. In view of the above it was deduced that
‘Pingguozao’was autotriploid. The RAPD fingerprints of‘Pingguozao’and‘Zanhuangdazao’were
different，which were two different natural triploid cultivars.

Key words: Ziziphus jujuba Mill., natural triploid, karyotype, pollen mother cell, meiosis