In order to study the role of JAR1(At246370)gene of Arabidopsis thaliana in response to Botrytis cinerea,jar1(SALK_030821),a loss function mutant of JAR1 was obtained from the Arabidopsis Biological Resource Center.Homozygous mutants were used as materials,the spore suspension of B.cinerea was inoculated on the leaves of homozygous jar1 mutants grown for 4 weeks.The disease index of leaves were estimated within one week after inoculation.The growth of fungus on the leaves,reference to the actin gene expression of B.cinerea actin,was analyzed by qRT-PCR.The results showed that the disease index of jar1 leaves was significantly higher than that in wild-type after inoculation with the pathogen from the second day.The results of qRT-PCR showed that the expression of B.cinerea actin in wild type plants was 6.9 times higher than that in the control,while the expression of B.cinerea actin in jar1 plants was 20.2 times higher than that in the control on the third day after inoculation.It is indicated that the propagation speed of the pathogen on the jar1 mutant leaves is significantly higher than in the wild-type.The results of this study preliminarily indicated that JAR1 gene was involved in the resistance regulation of A.thaliana to B.cinereal.