Behaviors Of The Chromosomes In Cell Divison And Kyrotype Of Beet Armyworm, Spodoptera Exigua H(?)bner

Beet armyworm, Spodoptera exigua Hubner, is a critical agricultural pest all over the world In recent years, the damage caused by beet armyvvorm in China increases year by year. So far, the work on the biology, chemical control, biological control and resistance of beet armyworm was carried out, but the study on chromosomes of this insect is scant)'.Employing air-dry preparation, surface-spread preparation, sliver-stained preparation, C-banding and G-banding technique and electron microscope technique, the morphological characteristics and behaviors of the chromosomes in the mitosis and meiosis of beet armyworm were studied. The further work about kyrotypes and bandings of chromosomes in mitotic early metaphase and synaptonemal complex in meiotic pachytene and submicroscopic structure of synaptonemal complex was carried out. The results are as following.1. The diploid chromosome numbers of male and female of beet armyvvorm were 2n=62. In mitotic early metaphase, sister chromatids could be observed lying side by side in parallel. The chromosomes had some associations of the chromatids, but did not display primary constriction. Beet armyworm possess holokinetic chromosomes. In mitotic metaphase, chromosomes were condensed to minute spherical body.2. In meiotic early zygotene, chromosomes whose one terminal converge at a pole of cell display bouquet configuration. Homologues pairings began at their two ends and it resulted in chromosome interlocking. The lengths of synaptonemal complexes increaseed from early meiotic pachytene to late pachytene. In diakinesis nuclei of male, the homologues displayed rings, crossed or end-to-end configurations. But in diakinesis nuclei of female, the homologues were oriented parallel without any chiasma connecting them. In meiotic metaphase I , chromosomes were maximally condensed to double half-ball or dumb-bell structures.3. Chromosome kyrotype in mitotic early metaphase showed that relative lengths of 31 chromosomes varied continuously. The chromosomes from 1st to 3rd displayed longer and their relative lengths were longer more than 4%. From 4th to 31st adjacent chromosomes exhibited low variability of relative length. In general, 10th and 21st chromosomes displayed secondary constriction. Kyrotype of synaptonemal complex in meiotic pachytene showed that relative length proportion of 1st bivalent and 31st was more than 2. From 6th to 26th, the relative length variability of adjacent two bivalents was less than 4 %.4. Synaptonemal complexes in meiotic pachytene displayed conspicuous C-banding and G-banding, but the bandings regularly distributed along the lengthwise chromosomes. The results of C-banding and G-banding in mitotic early metaphase was not clear. In pachytene nuclei by sliver-stained, two fluffy globular nucleolus could be seen.5. In this study synaptonemal complexes diaplayed two lateral elements in parallel, but central element was indistinct. Lateral element of synaptonemal complexes produced different numbers of chiasmata. At least one NOR-synaptonemal-complex existed in beet armyworm and its terminal was connected with nucleolus. Recombination nodules were also observed in synaptonemal complexes. Heterotypical sex synaptonemal complex was seen in female, but none in male. Beet armyworm had a WZ/ZZ sex chromosome mechanism.