Comparative Studies Between Zea Maize, Zea Diploperenni And Their Hybrids By Fluorescence In Situ Hybridization

180-bp repeats and TR-1 elements are major components of maize knob. These two repeats are reliable landmarks for identifying maize and its relatives and they are useful tools for investigating the phylogeny and evolution of maize and its relatives. Fluorescence in situ hybridization (FISH) was carried out on mitotic chromosomes of Zea diploperennis, maize inbred lines F102, F107, GB57 and their hybrids using knob-associated tandem repeats, 180-bp repeats and TR-1 elements, together with 45S rDNA as probes. The distribution patterns of the three repeated sequences were analyzed on parental chromosomes. In Zea diploperennis, knobs on the short arm of chromosomes 1 and 4 and on the long arm of the chromosomes 4 and 5 are composed predominantly of the 180-bp repeats. In addition, 180-bp repeats existed together with TR-1 elements were also detected on the short arm of chromosomes 2 and 5 and on the long arm of the chromosomes 2, 6, 7, 8 and 9. In maize inbred line F102, 180-bp repeats were present in chromosomes 7S and one homologue of chromosomes 8L. TR-1 elements appeared on satellite of chromosome 6 and no detectable hybridization site co-located with 180-bp repeats was observed in maize F102. In maize inbred line GB57, 180-bp repeats existed on the long arm subterminal of chromosomes 1, 2, 3, 4, 5, 6, 8. TR-1 elements were detected on the long arm subterminal of chromosomes 2, 3, 4, 6 and satellite and on the short arm of chromosome 7. In maize inbred line F107, the different signals of 180-bp repeats and TR-1 elements, which could be easily identified on prometaphase chromosomes, were not overlap on the knob of chromosome 6L. TR-1 elements were located on the submedian kinetochore and satellite of chromosome 6. 180-bp repeats appeared on the terminal of chromosome 7.Polymorphism of size, number and distribution of 180-bp and TR-1 signals were revealed among different chromosomes in these species and heteromophism existed between some homlogous chromosomes in the same species. Using these excellent landmarks, the interspecific hybrid of maize and Zea diploperennis were identified. According to the hybridization signals on chromosome positions, the origin of foreign idioplasm was confirmed. The results suggest that comparative analysis of 180-bp repeats and TR-1 elements may help understand the genome organization and the evolution in Zea. Knob-associated tandem repeats can play an inportant role in detecting the integration of foreign chromosome and the chromosomal activity.