Abstract: An in vitro-inoculation test was conducted for developing a new technique to identify tomato resistance to Tomato yellow leaf curl virus（TYLCV）. The tomato seeds of the TYLCV-susceptible‘Moneymaker’，‘Zhongshu 6’and‘Lichun’，and the resistant line AVRDC CLN 2123 A were cultured in the media of test tubes. The tomato microshoots（2.0–2.5 cm in length）of each cultivar were excised after 21–25 days cultivated，and their basal parts were dipped in solutions（OD₆₀₀ of 0.5）containing Agrobacterium tumefaciens EHA 105 transformed with the infectious clone for the TYLCV-[CN：SH2]for 1 min. The inoculated in vitro microshoots were monitored for development of TYLCD（Tomato yellow leaf curl disease）symptoms for 8 weeks post-inoculation. The symptoms of TYLCD started to appear on susceptible in vitro-inoculated tomato plants two weeks after inoculation.Four weeks later，the susceptible plants displayed severe symptoms of stunting，upward leaf curling and yellowing. Eight weeks later，the susceptible plants showed extremely serious TYLCD symptoms and resulted in the browning，necrosisor death. But all of the microshoots of resistant tomato line‘AVRDC CLN 2123 A’remained symptomless and continued the growth normally.Agarose gel showed PCR products（356 bp）amplified from DNA extracts of the plants of the susceptible cultivars except the resistant plants of line‘AVRDC CLN 2123 A’. These results indicated the high possibility to identify the resistance against TYLCV in tomato varieties or germplasms in vitro using tomato microshoots.

Key words: tomato, in vitro-cultured plant, Tomato yellow leaf curl virus, the infectious clone, disease resistance identification