Comparison of molecular cytogenetic and genetic analyses in accessions of the two biotypes of Vicia benghalensis L

In Vicia benghalensis two different biotypes, named A and B, had been observed which differed for several cytological, genetical and biochemical characters. In the present study 27 accessions of this species belonging to the two biotypes were investigated using different molecular analyses, supported by an attempt to produce hybrids between selected accessions. RAPD fingerprinting of the 27 accessions demonstrated that accessions belonging to biotype A show a high degree of genetic similarity, while the opposite is true for the accessions of biotype B. The total genomic DNA from one reference accession was used as a probe to Southern blots of the DNA extracted from all the accessions in use. This analysis demonstrated that cross hybridization among the DNA of the two biotypes occurs only to a limited extent. The chromosomal localization of 18S-5 . 8S-25S and 5S rRNA gene clusters was determined by in situ hybridization. The results indicate that the two biotypes differ in the position of one of the 5S rRNA gene clusters. This indicates a major chromosomal rearrangement. Cell synchronization experiments on two reference accessions suggested that the two biotypes might differ in the duration of the single phases of the cell cycle. Finally, in crossing experiments three pods were obtained which developed for only a few days and proved to bear no viable seeds. These results confirm the existence of two divergent gene-pools and demonstrate the reproductive barrier between the two biotypes, thus suggesting the possibility of a specific ranking. (C) Annals of Botany Company.