In the genus Lilium, plants obtained from crosses, especially between distant relatives, are not always hybrids because embryos can develop as a result of apomixis. These plants constitute genetic material of the maternal parent only. In this study, verification of hybrid status of plants which have been obtained from the crosses 'Marco Polo'xLilium henryi and 'Expression'xL. henryi was performed through the use of cytological and molecular cytogenetic methods. According to cytological analyses, all genotypes tested had 2n = 2x = 24 chromosomes. Genomic in situ hybridisation (GISH) was used for hybrid verification. In hybrid plants, this method distinguished all paternal and maternal chromosomes at the stage of somatic metaphase and prophase. For GISH, paternal genomic DNA was used as a probe and maternal DNAs were used as blocks. Fluorescence in situ hybridisation (FISH) with 5S rDNA and 25S rDNA probes was used as the second method of hybrid verification. Selected chromosome markers based on genome-specific localisation of rDNA loci were used for analysis of the F1 hybrids obtained from the crosses 'Marco Polo'xL. henryi and 'Expression'xL. henryi. The presence of marker chromosomes characteristic for each of the paternal genotypes was a confirmation that the plants obtained were hybrids.
We undertook an analysis of the genomic relationships between 15 isolates of Phytophthora ramorum Werres, de Cock et Man in't Veld, obtained from symptomatic plants growing in Polish ornamental nurseries, and 2 representatives of the European population and 3 of the North American population. Dendrograms were generated by UPGMA based on 786 amplification products obtained in ISSR-PCR reactions. The representatives of the European population and 13 of the "Polish" isolates formed a common cluster. The other 2 "Polish" isolates, which were found in 1998, and the 3 American representatives formed 2 separate clusters. There was no observed link between genomic distance on the basis of polymorphism and the origin of the isolates from plant species.
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