Molecular Cytogenetics Study For Coix L. And Its Closest Relatives

Eight coix species were used in this study. Isozyme analysis of peroxidase and polyphenol oxidase indicate the relationship among them; homologous degree and distribution characteristics of repetitive DNA sequences were analyzed on the chromosomes of Coix Lacryma-jobi L., Coix agrestis Lour and Coix aquatica Roxb by genomic in situ hybridization (GISH). The genetic stability of heterochromatic knob-associated tandem repeats in progeny of distant hybrid between maize and teosinte were studied using fluorescence in situ hybridization (FISH). The process of pollen mother cell (PMC) meiosis in teosinte hybrids"8493"was observed and their parental genetic relationship was discussed. Main results are the following:1. The contribution and activity of peroxide and polyphenol oxidase isozymes from Coix species(Coix Lacryma-jobi L.,Coix agrestis Lour and Coix aquatica Roxb) were analyzed by PAGE. The results showed that POD and PPO isozymes with high activity were abundant and complex.Enzyme lines were clear and stable. The differences between different species were distinct. Eight species of coix tried to gather into four kinds of cluster pictures by the analysis of peroxide isozyme. 1and 3 were grouped together; 4,5and 6 were grouped together; 7and 8 were grouped together; 2 was grouped singly. The results might be useful in determining different varieties of Coix L. and studying genetic relations.2. Genomic in situ hybridization (GISH) method was used to study differentiation and relationships between the Coix Species. The chromosomes of Coix Lacryma-jobi L, Coix agrestis Lour and Coix aquatica Roxb were hybridized with labelled probes genome from Coix Lacryma-jobi. (2n = 20). The GISH results indicate that the homology between Coix Lacryma-jobi L and Coix agrestis Lour genomes is very close. Twenty chromosomes from Coix aquatica Roxb genome are highly homologic with The chromosomes of Coix Lacryma-jobi L, concludes that Coix aquatica Roxb belongs to the same group of sextuploid Coix R.in Guangxi.3. Knob heterozygosity and stability in mitotic chromosomes of maize inbred 330, DP and alloplasmic pure line 540 were studied using the fluorescence in situ hybridization (FISH) technique with knob-associated tandem repeats (180 bp and 350 bp (TR-1)) as probes. The knobs gave strong hybridization signals and easily be identified. The results indicated the number of knobs reduced on the chromosomes of pure line 540 compared to its parents and possible reason of this change was discussed.4. Meiotic behavior of pollen mother cells in the hybrid of Perennial diploid teosinte and Annual diploid Euchlaena mexicana schrad"8493"were observed. The results indicated that at metaphases I and II there showed a small number of chromosomes scattered out side their equatorial plate, at anaphasesI and II there appeared chromosome bridges and lagged chromosomes in some pollen mother cells and at tetrad stage a few abnormal tetrad are visible, the pollen mother cells that abnormally acted made up about 11. 1%; 45s rDNA was located on the meiotic chromosomes of pachytene and diakinesis stage by fluorescene in situ hybridization (FISH), it showed that 45s rDNA was located on the same bivallents. The studies proved closing relationships between the parents of"8493".