| Three kinds of experiments, such as investigation on techniques in chromosome preparations, observations of meiotic behaviours and karyotype analysis on mitotic metaphase chromosomes were established to exploit the interspecific hybrid new species Cucumis X hytivus Chen & Kirkbride with the new species itself and its both parental cucumber 'Beijingjietou' and wild species C. hystrix Chakr as materials.(1) Techniques in chromosome preparation.Techniques of meiotic chromosome preparation for the new species, cucumber 'Beijingjietou' and allotriploid cucumber were discussed. Different requirements were found among the above 3 materials in sampling. Suitable fixation with Karnuo's solution for 2~24hr and storage in 75% alcohol were helpful in improving slide-making quality. Staining in decolored base fuchsin, decoloring with 20% or 45% acetic acid and warming on flame could improve the slide resolution. A complete set of slide-making procedures was established particularly for those 3 plants.Tendrils were ideal alternative materials for tendril producing species, such as Cucumis plants, in mitotic chromosome preparation, when resources were rare and seeded root-tips were unavailable. Tendrils were relatively more and easily available, and were necessarily to be processed differently when compared to root-tip as materials in chromosome preparations. The main difference existed in chromosome pretreatment and hydrolization. Chromosome number of the new species was firstly counted to be 2n = 38 with tendrils as materials.(2)Meiotic division.Meiotic divisions of different cultivated genotype cucumbers (including cucumber 'Beijingjietou') were evaluated. Specific characters for each meiotic division of PMC were briefly reported. The main chromosome configurations at metaphase I were circle-shaped bivalents. Seasonal stress such lower temperature on the formation of multi-spores at telophase II in common diploid cultivar was firstly discussed. And the special variation in the nucleus number and other abnormal meiotic behaviors in C. sativus var. xishuangbannesis was also firstly revealed in present paper.The meiotic divisions in the original diploid hybrids and in the original new species were observed. In PMCs of the diploid hybrids, the complete normal meiotic division was 2absent. 19 univalents were the main chromsome configurations at metaphase I . Chromosome lagging and spindle misorientation were frequently captured at anaphase I . In contrast, normal meiotic division procedures were observed in the chromosome-doubled interspecific hybrid. More than 90% configurations observed at diakinesis and M I were bivalents and less than 3% were trivalents and quadrivalents. Equal chromosome separation (19+19) at anaphase I , and chromosome lagging and unequal separation were coexisted. At anaphase II, chromosomes were separated equally into 4 groups at each pole with 19 chromosomes and formed a normal tetrad after telophase II.Chromosome number of the regenerated and seeded plants selfed from the new species was checked both stable at 2n = 38. Meiotic behaviors of regenerated plants from line Cl-33 and Cl-77 were found similar within the same line but different between the 2 lines. The 8 seeded plants were different greatly in meiotic behaviors. 1# plant was highest in diploidization degree and in bivalent percentage, and lowest in the frequency of chromosome laggd and uneaqueal separation. Genome separation was described at different stages in the5# seeded plant, which was most typical in the phenomenon. Two other types of microspores were forecasted with n = 7 and n = 12. The different effects of self-pollination and multiplication on the genetic stability of the new species and on the introgression of alien useful genes via the new species were discussed.Chromosomes configurations at meiotic metaphase I were 2n = 7II (CC) +121 (H) (C stands for cucumber genome, H for Cucumis hystrix Chakr. genome) and trivalents, formed by one pair of cucumber chromo...
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