To evaluate the disease resistance of Begonia × hiemalis Fotsch. ‘Schwabenland Red’ mutants induced byethyl methane sulphonate (EMS), we investigated the incidence and severity of stem rot caused by Rhizoctoniasolani Kuhn, and their morphological changes. In this study, we obtained three mutants with highly resistant diseaseafter two rounds of screening when the inoculated amount was 3 sheets/plant. The severity scale was 0 and therewere no obvious symptoms of stem rot in highly resistant Begonia × hiemalis. However, most of EMS mutagenizedplants were susceptible to stem rot caused by R. solani under this inoculated amount. In addition, these resistantmutants had different phenotypes as compared with the uninfected control plants. The color of leaves of the R. solani-resistent mutants was different with the control plants and their leaves were bigger than that of the control. The shape and number of their flowers were obviously different, as compared to the control plants.