Recurrent and Reciprocal Recurrent Selection in Sugarbeet1

Abstract

Five cycles of recurrent selection (RS) for general combining ability and two cycles of reciprocal recurrent selection (RRS) in sugarbeet (Beta vulgaris L.) were evaluated. The fifth‐cycle RS synthetic produced significantly less sucrose than its source population, but combined equally as well as its source population with a group of four male sterile tester lines. The reduced sucrose yield of this synthetic resulted entirely from reduced root yield, partially accounted for by the estimated 20% inbreeding of this synthetic. Three second‐cycle RRS synthetics were produced from each of two source populations (A and B). These synthetics were generated on the basis of superior progeny performance for recoverable sucrose, root yield, and sucrose content, respectively. Recoverable sucrose increased relative to its source only in the second cycle synthetic for root yield from source A. Root yield improvements were made in two synthetics from the low yield source A. Improvement in sucrose content was made in two synthetics derived from the low sucrose source B. In no synthetic was there a simultaneous increase in root yield and sucrose content. Crosses between the A and B synthetics did not significantly exceed the performance of the superior source parent for recoverable sucrose or any of its components, root yield, sucrose content, or thin juice purity. Reciprocal recurrent selection was successful in improving the general and specific combining abilty of those yield components that were relatively low in the sources. Simultaneous improvement of all components for production and for combining ability was not achieved by either of the two breeding methods.