A Screen for Arabidopsis thaliana Mutants with Altered Susceptibility to Heterodera schachtii

Genetic approaches are a powerful means to elucidate plant-pathogen interactions. An in vitro screening protocol was developed to identify Arabidopsis thaliana mutants with altered susceptibility to Heterodera schachtii, the sugar beet cyst nematode. In an initial screen of approximately 5,200 ethyl methanesulfonate-generated mutant plants, two stable mutations were identified. Both mutant lines were backcrossed and were found to harbor single recessive mutant alleles. Mutant line 2-4-6 shows an approximately two-fold increase in sedentary and developing nematodes, while mutant line 10-5-2 exhibits a significant decrease in susceptibility that manifests itself only after nematodes become sedentary. Analyses of progeny from crosses of lines 2-4-6 and 10-5-2 indicated that the two mutations are not allelic. However, the mutant gene in line 2-4-6 was found to be allelic to the previously identified mutant rhd1 and was termed rhd1-4. The mutant gene in line 10-5-2 was called asc1 for altered susceptibility to cyst nematodes. Our results demonstrate the feasibility of a nematological mutant screen and strengthen A. thaliana and H. schachtii as a model pathosystem.