Combining Ability and Gene Action Estimates in an Eight Parent Diallel Cross of Sugarbeet1

Abstract

Twenty‐eight F1 hybrids from an eight parent diallel cross grown at two nitrogen fertility levels were analyzed for type of gene action controlling 11 sugarbeet (Beta vulgaris L.) characters. Nonadditive genetic variance was of prime importance in controlling root weight under low and high nitrogen levels, accounting for 51% and 68% of the total genetic variance, respectively. For recoverable sugar, nonadditive genetic variance accounted for 67% and 83% of the total genetic variance under low and high nitrogen. Additive genetic variance accounted for most of the genetic variance for sucrose percentage and root/shoot ratio. Both additive and nonadditive genetic variance were significant for percent thin juice purity, but only at the high nitrogen fertility level.Additive genetic variance was predominant for six nonsucrose components of purified juice. In addition, significant amounts of nonadditive gene action were found for all six nonsucrose components at one or both nitrogen levels. Betaine was the least affected by change in nitrogen of all the characters measured.