Combining Ability in I₀ Single Crosses of Red Clover¹

A diallel cross involving 10 I 0 red clover ( Trifolium pratense L.) clones was evaluated for survival on two dates, total season yield in 1970, vigor, and days to first bloom on three different dates. General combining ability was the most important and the only significant source of genetic variance for all the characters. The additive genetic variance constituted 81% or more of the total genetic variance for each character. Nonadditive genetic variance may not be important enough to warrant production of hybrid red clover varieties, but other justifications exist. Parents for hybrids could be developed by selection and progeny testing, and little emphasis should be placed on examination of specific combinations among selected parents.