Beta vulgaris NC-7 Collection as a Source of High Sucrose Germplasm

Abstract

Among the major problems facing sugarbeet breed­ ers are lack of genetic diversity and the negative association between root yield and sucrose concen­ tration. The USDA-ARS Beta collection contains a wide array of material that has not been utilized fully. In this study 167 accessions of the NC-7 collec­ tion were evaluated for sucrose concentration on an individual root basis. A breeding population was formed by interpollinating 30 individuals with rela­ tively high sucrose concentration. Seed from each plant were harvested separately and progeny were evaluated the following year in replicated field plots. Subsequent selection was based upon both individual and family performance. Selected plants were interpollinated, seed were harvested again from individual plants and the progenies were evaluated as a family. This procedure was repeated in each of five selection cycles. After the second cycle it was apparent that root weight was decreasing drastically, so individual root weight was added to the selection criteria. The average sucrose concentra­ tion of fifth-cycle families was increased to 113 % of Ultramono. Five families combined high sucrose concentration with average root yield in the fourth and fifth selection cycles. This research indicates that germplasm collections of the USDA can be used for improving yield and quality of sugarbeet and for widening the genetic base of the sugarbeet crop.