Effect of species environment on host preference of Cuscuta campestris

Abstract

Cuscuta campestris is one of the most widespread and most harmful parasitic plants in the world. It regularly infests economically important crops substantially reducing their yield. Its host preference has been frequently investigated in natural habitats, but studies have usually been performed at only one site. In this study, I tested the hypothesis that host-preference studies performed at a single site provide information only about local individuals of the host species and not about the species of hosts in general. The preferential status of host species was investigated in different geographical regions, in different species environments. Altogether 1847 relationships between parasite and plant species were examined and categorized at 171 places in Hungary. The used method took into account the frequency and intensity of infestations on the hosts, the proportion of resource use and availability, the resource distribution as well as the defence mechanisms of the hosts. The frequency and intensity of infestations greatly varied amongst the 174 detected host species. The results confirmed that frequently parasitized hosts of C. campestris are not necessarily preferred. Most host species have infestations of varying intensity in different species environments. Poaceae species were found to differ from each other in the extent to which they support the parasite’s growth. The study revealed also that C. campestris does not always develop haustoria on individuals of those species, which are unable to contribute significantly to its growth.