The objective of this research was introduction of chit42 to tuber mustard plants through Agrobacterium- mediated transformation against white mold caused by Sclerotinia sclerotiorum. The binary plasmid pGisPEC1 was used in this study. Polymerase chain reaction analysis detected the transgene in 27 transformants with a transformation efficiency of 6.9%. Southern blot test was used to assess the copy number of transgene in tuber mustard plants. One, two, two, and two chit42- related bands were observed in the transformed lines TMB4, TMB7, TMB12, and TMB18, respectively. Enzymatic tests showed a significant increase in the activity of endochitinase in protein isolated from leaf tissues of chit42 transgenic 75-day tuber mustard lines. The pathogenicity of three pathogen isolates was tested on the leaves of transformed plans. The results of current study showed that expression of the gene chit42 in tuber mustard plants markedly reduced infection radius on the leaves 7 days after inoculation with the fungus.