Modification of Seedstalk Development and Its Effects on Seed Yield and Seed Quality in Carrot (Daucus carotaL.)

ABSTRACT Carrot (Daucus carota L.) seeds vary greatly in maturity as a result of umbel order formation on the mother plants. The objectives of this study were to investigate the possibility of using chemical growth regulators as chemical pruning agents to modify seedstalk development in carrot plants, and to determine the effect of such modification on seed yield and quality. The number of days to primary umbel anthesis was unaffected by application of growth regulators. Seedstalk height was increased by GA3 and reduced by ancymidol or daminozide. The decrease in seedstalk height was linear with the increase of ancymidol concentrations from 25 to 100 ppm and quadratic when daminozide (1000 to 8000 ppm) was used. Ancymidol and daminozide were effective in reducing total number of branches per plant and were effective in reducing the number of tertiary umbels. Total seed yield was reduced by ancymidol and daminozide compared to the control. When compared to hand pruning, ancymidol and daminozide generally had no effect on total seed yield. The distribution of seed yield between umbel orders was shifted in favor of primary and secondary umbels by daminozide. Hand-pruning eliminated seed from the tertiary umbels. Seed germination and seed quality were not improved either by chemical or hand pruning, despite the reduction of total number of umbels by both methods. The best seed quality was in fact found in seed from tertiary umbels. Delaying carrot seed harvest until tertiary umbel seeds reach maturity is recommended to increase seed yield and gain improved seed quality.