4 pairs of allelic lines that had different difference of diameter at top and base of main stem were used for yield test of six years.The results showed that average yield of indeterminate-semideterminate lines was more than that of semideterminate-indeterminate lines in normal or dry years,on the contrary in more rainfall years.Average yield of more difference type was 3.5 percent higher than that of less difference type in six years,that difference of two group was extreme significant by t-test.Yield fluctuation index was less than 5 percent.Allelic lines of more difference type had better suitable ability for experiment environment.So,difference of diameter at top and base of main stem should be essentially differentiation characteristic.