Abstract: The reciprocal crosses had been conducted among the adopting Begonia rex and wild Begonia from Yunnan or horticultural breeds of Begonia rex . The characters and properties of the F1 generation on the leaf mottling , cauline type and cold resistant capacity were observed. The segregation of green mottling character was studied by observation and statistic analysis of the F2 populations. The results showed that the silvery green mottling and without mottling were one couple of contrast characters of Begonia rex , the silvery green mottling was dominant , the genetics of this couple of characters
was correspond to Mendel’s law. In the F1 plants of B . rex ×B . longialata , the continuous expression of the silvery green mottling was influenced by the intensity of illumination. To keep the primary color of silvery green mottling , it was need to add 2000 lx illumination after two years of growth. Rhizome was the most steady genetic character , its genetic retention rate was 90 %. High heterosis was showed in F1 generation on the cold resistance , F1 population possessed a higher cold resistance capacity than their parents. This paper provided a reference for the selection and breeding of green mottling
character and cold resistance.

Key words: Begonia rex, Sexual hybridization, Genetic property, leaf mottling