Seedlings of the F1 plants derived from the crosses of Japanese mulberries with Thai and Indian (Kashmir’s) mulberries were subjected to comparison to the cross within Japanese cultivars regarding shoot sprouting, shoot growth, rooting ability and nutrient value for feeding silkworms. The F1 seedlings of the crosses between Thai or Indian mulberries and Japanese cultivars were superior in all these characters to the cross within the Japanese materials. This result indicates that genetic improvements could be achieved by transmitting such superiority of Thai and Indian cultivars to Japanese mulberries.