Cytokinin regulation of flower and pod set in soybeans (Glycine max (L.) Merr.)

Exogenous application of cytokinin to raceme tissues of soybean (Glycine ma x (L.) Merr.) has been shown to stimulate cower production and to prevent f lower abortion. The effects of these hormone applications have been ascerta ined for treated tissues, but the effects of cytokinins on total seed yield s in treated plants have not been evaluated. Our objectives were to examine the effects of systemic cytokinin applications on soybean yields using an experimental line of soybeans, SD-87001, that has been shown to be highly s ensitive to exogenous cytokinin application. Soybeans were grown hydroponic ally or in pots in the greenhouse. and 6-benzylaminopurine (BA) a as introd uced into the xy]em stream through a cotton wick for 2 weeks during anthesi s. After the plants had matured, the number of pods, seeds per pod. and the total seed weight per plant were measured. In the greenhouse. application of 3.4 x 10(-7) moles of BA resulted in a 79% increase in seed yield compar ed with controls. Results of field trials showed much greater variability w ithin treatments, with consistent, but non-significant increases in seed nu mber and total yields of about 3%. Data suggest that cytokinin levels play a significant role in determining total yield in soybeans, and that increas ing cytokinin concentrations in certain environments may result in increase d total seed production. (C) 2001 Annals of Botany Company.