transient expression of a candidate effector gene in host plants following Agroinfiltration is a useful method to investigate the role of the gene in pathogenecity. In this study, the effects of two Agrobacterium tumefaciens strains on four standard melon lines and two Iranian melon cultivars were investigated to establish transient expression in melon. Compatibility of the LBA4404 and GV3101 strains was defined by injection of the bacterial suspensions into the leaves of cultivars. Viability of the injected Agrobacterium strain cells in leaf tissues was evaluated 24 hours after injection by prokaryotic GUS reporter gene assay. The LBA4404 strain harboring the pCAMBIA3301 vector containing an intron-GUS reporter gene was used to confirm eukaryotic GUS expression in the plant cells. The LBA4404 strain was transformed by the pBI121 and pCAMBIA3301 expression vectors and transient transformation was confirmed by colony PCR technique using the PSh3-F/R primers. The efficiency of transient transformation of the melon leaves was evaluated 48 hours after Agroinjection of the LBA4404 strain containing pCAMBIA3301 by the histochemical GUS assay. The leaves that were injected by LBA4404 harboring pBI121 showed GUS activity. All the melon cultivars transiently expressed the GUS reporter gene 24 hours after Agroinjection. These findings could be used in the future studies to evaluate function of candidate effector genes in interaction with standard melon lines.