1. To breed the excellent varieties of tomatoes for manufacturing 13 combinations were crossed among Italian tomato strains such as "SM 1", "SM 2", "SM 3", "A.SM", "Roma" and "Italian C_1". And their properties, especially yielding abilities, were investigated. The results are as follows :
2. 11 hybrids in 13 combinations manifested "hybrid vigour". Among these F_1 plants the F_1 of "ASM×Italian C_1" was excellent and its increasing rate of yield amounted to 24.6%.
3. Another 2 hybrids by combinations such as "SM 3 × ASM" and "SM 2 × Italian C_1" did not manifested "hybrid vigour". According to this result it is assumed that the parents of these two combinations are the same strain respectively. But about this, a supplementary examination would be tried.