Polyploid and maternal effects on Rhizoctonia root rot resistance in sugarbeet

Summary Three sugarbeet breeding lines partially resistant to the root-rotting fungus, Rhizoctonia solani, were converted to the tetraploid condition without selection. These three diploid and tetraploid lines were crossed with three diploid male-sterile lines to produce equivalent diploid and triploid hybrids. The triploid hybrids were significantly more resistant to Rhizoctonia than were the diploid hybrids. However, the tetraploid resistant limes were no different than their diploid equivalent lines. Reciprocal crosses provided no evidence of maternal effect on resistance. Cytoplasm that included the male-sterility factor had no influence on resistance. Triploid hybrids, where the resistant parent is tetraploid, should be advantageous in the breeding of rhizoctonia-resistant hybrid varieties.Joint contribution of the Agricultural Research Service, U.S. Department of Agriculture, the Colorado State University Experiment Station, and the Beet Sugar Development Foundation. Published with the approval of the Director of the Colorado State University Experiment Station as Scientific Paper Series No. 2072.