| Chromosome is the carrier of biotic genetic material, and its structure has the feature of relative constancy. So, through the study of chromosome, we can get the disclosure of the structural differences among organisms, and the reflection of the hereditary diversity and the systematic evolution route of the creatures. Cytogenetics, which focus on the research of chromosome, is the product of the reciprocal chiasmata and combination of genetics and cytology, it aims to demonstrate basic science of organic heredity and variation cytology. The study of insect chromosome can enrich the theory meaning and knowledge system of insect genetics, and reveal the natural rules of species succession, interspecific evolution, and intraspecific evolution of insect. Meanwhile, the study can also offer new method and technique to establish insect taxonomical system, specification of kindred, and subspecies identification. Moreover, it can be made the use of the genetic management of pests, and offer the new way to explore the mechanism of pest resistance to chemicals.Helicoverpa armigera (Hiibner) and H. assulta (Guenee) are critical agricultural pests in China, Their interspecific hybrid can reproduce. In order to reveal the genetic rules between the two pests, we took a study of the chromosome of H. armigera and H. assulta, which contained the contents as following: the karyotype feature, the behaviors of the chromosome during the period of mitosis and meiosis, synaptonemal complex, chromosome variance, and F1 generalization comparison.1 With the method of HSG-banding and normal C-binding technique, we made an analysis of the karyotypes for H. armigera and H. assulta during the period of mitosis metaphage and meiosis pachytene. The result showed that the numbers of haploid of H. armigera and H. assulta were all 31, part of chromosomes were of the kind of holocentromere. The chromosome length of H. armigera ranged from 1.64un to 5.99um. With Lima-De-Faria as the standard, there were 7 middle-sized and 24 small-sized chromosomes among all its haploid. The chromosome length of H, assulta ranged from 1.27 um to 5.01 Mm. The chromosome length of H, assulta was shorter than that of H, armigera, and there was very significant difference between the two pests from the result of variance analysis, there were 5 middle-sized and 26 small-sized chromosomes among all its haploid.Comparatively speaking, 80% numbers of the chromosomes of H, armigera in split phase were 31, whereas, there are only 50% were 31 in the case of H. assulta. Consequently, it demonstrated that the chromosome polymorphisms of//, assulta turn out to be much more obvious, and the chromosome of//. armigera was relatively stable.2 Through the analysis of the mitosis of egg and the meiosis of auxocyte, it appeared no significant difference of chromosome behavior in these procedures.3 For H. armigera and H. assulta, we got a clear show of the shape and construction of synaptonemal complex's lateral element and central element; The analysis of synaptonemal complex karyotype showed that, in the body of H. armigera and H. assulta, the number of synaptonemalcomplex among haploids were all 31, and it also turned out that the lengths of synaptonemal complex of H. armigera and H. assulta showed no significant difference according to variance analysis. The correlation analysis of the lengths in pachytene and the synaptonemal complex of the two pests showed that the two had an obvious linear dependence. So, the method that tries to take the place of meiosis pachytene by synaptonemal complex is feasible.4 The chromosomes of H. armigera and H. assulta can not be detected correctly during staining flaking of C-band and G-band. Whereas, we can find heterotypic chromosome -sex chromosome in female synatonemal complex when doing the analysis of synatonemal complex. With the further analysis, we determined that the longer one is chromosome W, and the shorter one is chromosome Z. According to all the work we have done above, it fairly verified the law that the sex... |
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