| Popis: |
The research described in this thesis deals with chromosome identification and gene mapping. In contrast to results from literature, in this study only three chromosomes (1, 2 and 12) could unambiguously be identified in mitotic cells using conventional staining, and four (1, 2, 3 and 4) in case of Giemsa C-banding. With both methods the chromosomes 1 and 2 could unambiguously be identified and are homologous to the chromosomes 1 and 2 as identified by pachytene analysis. Reliable chromosome identification in potato can be achieved by pachytene analysis.It was found in this study by using non-radioactive in situ hybridization that one basic chromosome of the potato contains rRNA genes. In contrast to a report in the literature about detection of one chromosome with gene(s) for patatin using a cDNA clone, hybridization with a genomic DNA clone used in this study detected more than one basic chromosome carrying genes related to patatin.The bivalents in S. phureja Juz. et Buk. were morphologically very similar to those of S. tuberosum L. ssp. tuberosum Hawkes cv. Gineke as identified by pachytene analysis. An interchange in S. phureja is described and the involvement of the chromosomes 3 and 12 in this interchange could clearly be demonstrated by pachytene analysis and the meiotic behaviour in F 1 hybrids. Trisomic descendants selected in the first selfed generation of the interchange heterozygote were primary trisomic being homozygous for the interchange or tertiary trisomic.Meiotic behaviour in 11 primary trisomics was investigated and female transmission of the extra chromosome determined. Triple synapsis of pachytene chromosomes was often found in the euchromatic parts of the chromosomes. In this study a significant correlation between the relative chromosome or euchromatin length and the coefficient of realization of a trivalent at metaphase 1 was found in the primary trisomics of the potato. In spite of this result no relationship could be established between female transmission and the length of the extra chromosome.By means of half-tetrad analysis the map distance relative to the centromere could be estimated of each of three dominant genes involved in resistance to potato viruses X and Y and to pathotype Ro1 from Globodera rostochiensis , and of the recessive gene for yellow leaf- margin. The gene for yellow margin was localized on chromosome 12 and that for topiary on chromosome 3 by means of trisomic analysis. |
