from the cytoplasm, and the rapid alternation in genome organization [100]. These peculiar features are
most probably involved in some way in the evolution and development of parasitic plants. The chondri-
ome contains genes for the translation apparatus of the mitochondrion as well as those coding for subunits
of the respiratory chain complexes. In our study we included representatives of both groups.
The rrn5, rrn18, and tRNAfMetusually represent one cistron. In our investigation its sequence was
present in all the investigated genotypes. Hybridization data show the same situation for coxIII, atp9, and
atpA sequences. The way of life of parasitic plants allows the dropout of a large amount of biochemical
pathways. Nevertheless, changes in the preceding genes detectable by Southern blot analysis have not ac-
cumulated, which could be due to the direct need for their products (cytochrome coxidaze subunit III,
subunits 9 and A of the ATPase complex) in the life cycle of the plants.
D. Polymorphism in 18S Ribosomal DNA—a Genetic and Molecular
Markerrrn18unambiguously distinguishes between three O. ramosagenotypes (seeds collected from Spain,
Nothern America, Bulgaria) on the one hand and O. aegyptiacaandO. oxylobaon the other with all four
restriction endonucleases and in the three generations of plants used in the study. Therefore it can be used
as a molecular and genetic marker to discriminate between these species. The three distinct genomes of
plants each contain a complement of ribosomal RNA genes. It has been shown that the nuclear 18S rDNA
PARASITIC FLOWERING PLANTS OF GENUS OROBANCHE 795
Figure 4 Southern blot of Orobanchesp. DNA digested by EcoRI, probed with mitochondrial gene cox III.
1, Lambda HindIII; 2,3, O. ramosa, Spain; 4,5, O. aegyptiaca, Egypt; 6,7, O. oxyloba, Egypt; 8,9, O. ramosa,
Bulgaria; 11, O. ramosa, North America; 12,13, L. esculentum.