Breeding for Resistance to the Sugarbeet Root Maggot1

Thirty‐six genetically diverse sugarbeet (Beta vulgaris L.) lines were evaluated to determine their potential resistance to the sugarbeet root maggot, Tetanops myopaeformis Roder. Significant and relatively consistent differences in maggot damage were noted over 3 years. Damage ratings of F1 crosses of resistant ✕ susceptible lines tended to be intermediate between those of the parents. Selection for high‐ and low‐maggot damage showed a linear trend in increasing and decreasing maggot damage, respectively. The average decline in the low‐damage selection was approximately 5% per cycle. After five cycles of selection, there was no change in the rate of decline, indicating that further selection progress can be made. A greenhouse test confirmed field designations of resistant and susceptible genotypes. A low‐damage inbred had lower maggot survival, smaller maggot weight, lower damage ratings, and greater root weight than a susceptible line.