Botrytis cinerea is a ubiquitous necrotrophic fungal pathogen that infects over 200 different plant species. We have analyzed 17 Arabidopsis ecotypes for natural variations in their susceptibility to B. cinerea, and found compatible and incompatible Arabidopsis–Botrytis interactions. We determined that Arabidopsis ecotype Ler is resistant to 5 B. cinerea isolates used in this study. To further investigate the roles of the salicylic acid (SA)-dependent defense response pathways against B. cinerea, we inoculated various Arabidopsis mutants with the pathogen. Arabidopsis Ler plants expressing the nahG gene inoculated with B. cinerea showed as much resistance as the parental plants (Ler-wild type). The sgt1b-1 and rar1-10 mutants also showed resistance to the pathogen. In this study, we discuss the natural variations in the symptoms observed among various ecotypes upon inoculation with B. cinerea. In addition, SA plays only a minor role in preventing systemic infection with B. cinerea.