Indirect Effects of Recurrent Selection for Fe Efficiency in Soybean

Genetic improvement for Fe efficiency was achieved in the soybean [Glycine max (L.) Merr.] population AP9 by recurrent selection. The purpose of this study was to evaluate possible indirect effects of recurrent selection for Fe efficiency on plant and seed traits. Parents of the Cycle 0 (C0) through Cycle 7 (C7) populations were evaluated in replicated tests over 2 yr on noncalcareous soil. There was a significant linear increase in yield of 1.4 g m⁻² cycle⁻¹, height of 2.6 cm cycle⁻¹, and lodging of 0.I score cycle⁻¹. There were significant linear decreases in seed wt. of 1.9 mg seed⁻¹ cycle⁻¹ and seed oil of −0.6 g kg⁻¹ cycle⁻¹. Seed-filling period decreased linearly an average of −0.2 d cycle⁻¹. There were no significant linear changes in time of maturity, seed protein percentage, length of flowering period, leaflet area, leaflet wt., or specific leaflet wt. There was a significant linear change in three of the five fatty acids in the seed oil. Palmitic and linolenic acids increased 1 g kg⁻¹ cycle⁻¹, and oleic acid decreased 2 g kg⁻¹ cycle⁻¹. There were no significant linear changes in stearic or linoleic acids. A micronutrient analysis of the seed from C1 and C7 indicated that the average content of Fe was significantly greater in C7 and that the content of P was significantly greater in C1. There were no significant differences between C1 and C7 in the micronutrients B, Na, Mn, K, Ca, Mg, Zn, or Cu. The data obtained in this study indicate that, with the possible exception of an increase in lodging, the AP9 population has not been deleteriously affected by selection for Fe efficiency. Contribution from the Iowa Agric. and Home Economics Exp. Stn., Ames. Project no. 2475, Journal Paper no. J-12907. The research was supported in part by a grant from the Iowa Soybean Promotion Board.