Narrow-sense hcritability estimates, adjusted to account for inbreeding of parental lines, wcrc compared with realized hcritabilitles obtained by actual selection for high and low resistance to Cercospo~a beticola in sugarbeet (Beta vulgaris). Parental, F1, F~, F~, and polycross populations from high and low selections were field grown under an artificially induced leaf spot epidemic. Heritability estimates, in percent were 24.3___2.9 and 24.3___2.4 for each of two resistant X susceptible crosses. These values were compared with realized heritabilities of 20.47 and 26.71 for the same two resistant X susceptible crosses. Environmental variation accounted for 44 to 62% of the total variation for leaf spot resistance.

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Luther VV. La\\"son. Agricultural Research Technicians. in conducting breeding. evaluation, and other work at Fort Collins, Colorado, ;~ acknowledged. Pa.rticipation by other agencies and research personnel, in conducting' cooperative, varietal, evaluation tests, is indicated elsewhere in lhis report. Publication has been approved by the Director, Colorado Agricultural Experiment Station, as Scientific Series Paper ~o. 1099.