Host differentiation in Orobanche foetida Poir

Orobanche foetida Poir. is a parasitic plant widely distributed in the Western Mediterranean area. It typically parasitizes wild plants but has recently been described as an agricultural problem in legume crops in Tunisia. The pattern of genetic variation within and among O. foetida populations growing on chickpea and faba bean was analyzed by RAPD markers. The UPGMA cluster analysis based on Dice distance matrix showed a clear differentiation among O. foetida samples collected on chickpea and those on faba bean, suggesting a host-differentiation process. Although an AMOVA analysis revealed substantial internal variation among individuals within O. foetida populations (69.8%), there was a significant divergence between parasites on the two hosts considered (30.2%). Moreover, germination of O. foetida seeds collected on chickpea and faba bean in the presence of both host roots was studied. Germination percentages of O. foetida seeds varied depending on the host used both for collecting the seeds and evaluating the trait. According to these results, possible explanations for the origin of this new weedy parasite and the host differentiation process are discussed.