Differential induction of Orobanche seed germination by Arabidopsis thaliana

Parasitic plants, including the root holoparasites Orobanche spp., cause devastating damage to crops worldwide. Arabidopsis thaliana (L.) is widely used an amenable model for the study of plant biology, including plant-pathogen interactions. Bringing the two plants together in a controlled system will enable the study of the molecular and genetic basis involved in host-parasitic plant interactions and should provide tools for the detection of genes responsible for incompatibility and resistance responses. The objective of this study was to screen Arabidopsis lines for reduced germination of Orobanche seeds. A 96-cell well bioassay was developed to test the potential of lines, ecotypes and mutants of Arabidopsis to induce germination of Orobanche. Screening of 50 A. thaliana ecotypes did not reveal non-inducing ecotypes. Screening of 13000 A. thaliana fast neutron mutated M2 plants detected 94 non-inducing mutant plants of which 34 were rescued, self pollinated, and M3 seeds collected. M3 seedlings from five lines were reduced in their ability to induce germination. In a separate assay, we determined that the reduced germination rates corresponded with reduced distance from the roots at which germination occurred. While further studies are necessary to determine the segregation of low germination phenotypes, these lines might prove useful for studying the genetic basis of variation in germination stimulant production in A. thaliana.