Genetic Studies Of The Tri-species Hybrid And Maize-Tripsacum Addition Line

In this study, four materials were used as research materials, including Zea mays ssp. mays, Zea perennis, Tripsacum dactyloides L., and the tri-species hybrid (MTF-1). Used 5S rDNA and 45S rDNA as probes, the numbers and position of 5S rDNA and 45S rDNA on the chromosomes were obtained by FISH. Meanwhile, the derivative of Maize-Tripsacum was studied its chromosome composition and genetic behavior. The results were as follows:The result of FISH based karyotype analysis showed physical location of 5S rDNA and 45S rDNA were detected in genomes of Zea mays ssp. mays (2n= 40), Zea perennis (2n= 40), Tripsacum dactyloides L. (2n= 72) and the tri-species hybrid (MTF-1) (2n= 76). The hybridization signals of 5S rDNA and 45 S rDNA were respectively located on the subterminal regions of the long arms of chromosome 2 and the seeondary constriction region at the short arms of chromosome 6 in Zea mays ssp. mays. The hybridization sites of 5S rDNA and 45 S rDNA were respectively located on the subterminal regions of the long arms of chromosome 4,6 and the seeondary constriction region of the short arms of chromosome 11,13 in Zea perennis. The hybridization signals of 5S rDNA and 45S rDNA were respectively located on the submdian centromere region of the short arms of chromosome 6, 12 and the seeondary constriction region besides satellite at the short arms of chromosome 16,32 in Tripsacum dactyloides L. The chromosome number of the tri-species hybrid (MTF-1) was 76, its genomes contain three pairs of 45S rDNA and three pairs of 5S rDNA, the result of FISH showed the tri-species hybrid (MTF-1) was an allohexaploid, and further inferred the tri-species hybrid (MTF-1) is made from corn-tripsacum hybrid F1 (2n= 20Mz+36Tr) as unreduced gametes (n= 56) and tetraploid perennial Zea as normal male gametes (n= 20) together with development.The cytological analysis showed chromosome number of the alien addition lines was counted to be 21, besides of the normal chromosome pairs 10, it has an additional chromosome which is little shorter than 10 chromosome, and displayed submetacentric chromosome. The mitotic chromosomes of the addition lines were identified by GISH, the result showed that it was maize-tripsacum monosomic alien addition line, and occurrence of tripsacum-maize chromosome segment translocation. Morphological characters investigation showed that the addition line (2n= 21) was similar to the normal maize, but plant height was significantly lower than the corresponding diploid plants (2n= 20). Microscopic examination of pollen mother cells showed that there are mainly two configurations at diakinesis, as follow:10â…¡+1â… ,9â…¡+1â…¢, and the average meiotic configuration was 0.57â… +9.58â…¡+0.43â…¢. In addition, there are other abnormal chromosomes during division, lagging chromosomes and bridge. The stainability of the addition lines pollen grains immersed was only 4%, basic infertility, while the normal diploid pollen grains immersed was up to 98%. Transmission rate of alien addition line analysis showed that the highest transmission rate was 55.7%, the lowest was 42.0%, and the average of transmission was 46.44%.