Evaluation of IDC and Agronomic Traits Over 4 Cycles of Recurrent Selection for IDC Tolerance in Soybean.

An intermated population was developed for improvement of tolerance to iron-deficiency chlorosis (IDC) in soybean. Evaluation and selection in each cycle was for IDC tolerance only.  Progress for tolerance to IDC over four cycles of recurrent selection, as well as changes in agronomic traits, were evaluated in 6 environments over three years.  The 10 parent lines of each of the four cycles were evaluated together in a randomized complete block design in three replications in each environment.  Cycle means for IDC and other traits were determined based on the mean performance of the parents of that cycle.  Response to selection was determined by regression of the trait values on cycle number.